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1. A vessel and its contents of total heat capacity 120 J K  –1

 were heated using a methane

 burner. Calculate the maimum theoretical temperature rise when 0.10 g of methane was

completely burned. !he standard enthalpy of combustion of methane is

 –"#0 $J mol –1

.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

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(Total 4 marks)

2. %hen cycloheanol& C'(

11)(& is completely burned in oygen& the products are carbon dioide

and water.

%rite an e*uation to represent the reaction that occurs during the measurement of the enthalpy

change of combustion of cycloheanol.(Total 1 mark)

3. !he table below includes some values of standard enthalpies of formation +∆ H  ,.

-ubstance (2)+l, i)(+s, i+s,

∆ H   /$J mol –1  –2"' –" 0

!he standard enthalpy of solution of lithium hydroide is given below.

i)(+s, → i+a*, + )(

 – +a*, ∆ H    3 21 $J mol

 –1

+a, -tate why the standard enthalpy of formation of lithium is *uoted as 4ero.

.....................................................................................................................................(1)

+b, %rite an e*uation for the chemical reaction which represents the formation of lithium

hydroide from its elements& in which the enthalpy change is e*ual to its standard

enthalpy of formation.

.....................................................................................................................................(2)

+c, %rite an e*uation& including state symbols& for the reaction of lithium with water in

which lithium ions are formed.

.....................................................................................................................................(2)

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+d, 5se the data given above to calculate a value for the enthalpy change for the reaction of

lithium with water.

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.....................................................................................................................................

.....................................................................................................................................

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(Total 8 marks)

4. +a, 6plain the meaning of the terms mean bond enthalpy and standard enthalpy of

 formation.

 Mean bond enthalpy .................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Standard enthalpy of formation ...............................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(5)

+b, -ome mean bond enthalpies are given below.

7ond 8–( 8–8 8≡ 8 (–) )–)

9ean bond enthalpy/$J mol –1 :"" 1': # ': 1'

5se these data to calculate the enthalpy change for the following gas;phase reaction

 between hydra4ine& 82(& and hydrogen peroide& (2)2

(

 8

(

( (

 8   2 (    )    )    ( 8 ≡ 8 (    )    (

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+c, -ome standard enthalpies of formation are given below.

 82(+g, (2)2+g, (2)+g,

< H f = /$J mol –1 > –1:: –22

!hese data can be used to calculate the enthalpy change for the reaction in part +b,.

 82(+g, 2(2)2+g, ? 82+g, (2)+g,

+i, -tate the value of < H f 

=

 for 82+g,.

...........................................................................................................................

+ii, 5se the < H f =

 values from the table to calculate the enthalpy change for thisreaction.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

(4)

+d, 6plain why the value obtained in part +b, is different from that obtained in part +c,+ii,.

......................................................................................................................................

......................................................................................................................................(1)

(Total 13 marks)

5. 9ethanol& C(:)(& is a convenient li*uid fuel.

+a, An eperiment was conducted to determine the enthalpy of combustion of li*uid

methanol. !he energy obtained from burning 2.12 g of methanol was used to heat 1>0 g

of water. !he temperature of the water rose from 2#" K to :'2 K. +!he specific heat

capacity of water is .1" J K  –1

 g –1

,

+i, @efine the term standard enthalpy of combustion.

+ii, 5se the data above to calculate a value for the enthalpy of combustion of one mole

of li*uid methanol.(7)

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+b, 9ethanol can be synthesised from methane and steam by a process that occurs in two

stages.

Stage 1 C(+g, (2)+g, :(2+g, C)+g, is ∆  H =   2 0 ' $ J m o l – 1

Stage 2 C)+g, 2(2+g, C(:)(+g, ∆  H =   – # 1 $ J m o l – 1

  !he standard enthalpies of combustion of carbon monoide and of hydrogen are

 –2": $J mol –1

 and –2"' $J mol –1

& respectively. 5se these data and the enthalpy change

for Stage 2 to calculate a value for the standard enthalpy of combustion of gaseous

methanol.(3)

 (Total 10 marks)

6. +a, @efine the term standard  enthalpy of formation.

(3)

+b, -tate (esss aw and use it& together with the data given in the table below& to calculate

the standard enthalpy change for the following reaction.

9g)+s, 2(Cl+g, →  9gCl2+s, (2)+l,

9g) (Cl+g, 9gCl2 (2)

∆ H f  /$J mol –1  –'02 –#2 –'2 –2"'

(4)

+c, Bn an eperiment& an ecess of solid magnesium oide was added to >0 cm: of

:.0 mol dm –:

 hydrochloric acid. !he initial temperature of the solution was 21 C. After

reaction& the temperature had risen to >: C. +!he specific heat capacity of water is

.2 J K  –1

 g –1

,

5se this information to calculate the enthalpy change for the reaction of one mole of

magnesium oide with hydrochloric acid. Dor your calculation you should assume that all

the heat from the reaction is used to raise the temperature of >0 g of water.(8)

(Total 15 marks)

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7. !he table below contains some mean bond enthalpy data.

7ond (  ( C  C C3C  8≡ 8 8  (

9ean bond enthalpy / $J mol –1 :' :" '12 # :""

 

+a, 6plain the term mean bond enthalpy.

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(2)

+b, +i, %rite an e*uation for the formation of one mole of ammonia& 8(:& from its

elements.

.....................................................................................................................

+ii, 5se data from the table above to calculate a value for the enthalpy of formation of

ammonia.

.......................................................................................................................

.......................................................................................................................

.......................................................................................................................

.......................................................................................................................(4)

+c, 5se the following e*uation and data from the table above to calculate a value for the

C–( bond enthalpy in ethane.

( (( (

C C((C C (   ∆  H    3 – 1 : ' $ J m o l(

( (( (

 – 1

...............................................................................................................................

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...............................................................................................................................

...............................................................................................................................(3)

(Total 9 marks)

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8. +a, %rite an e*uation for the complete combustion of propanone& C:(')& to form carbon

dioide and water.

.....................................................................................................................................(1)

+b, Bn a laboratory eperiment& 1.> g of propanone were burned completely in oygen. !heheat from this combustion was used to raise the temperature of 100 g of water from

2#:.1 K to :>1.2 K.

+i, Calculate the number of moles of propanone in the 1.> g.

...........................................................................................................................

...........................................................................................................................

+ii, Calculate the heat energy re*uired to raise the temperature of 100 g of water from

2#:.1 K to :>1.2 K.

+!he specific heat capacity of water is .1" J K  –1 g –1,

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

+iii, (ence& calculate a value& in $J mol –1

& for the enthalpy of combustion of propanone.

...........................................................................................................................

...........................................................................................................................(5)

+c, Bn a similar eperiment& the enthalpy of combustion of butanone& C(")& was found to be

 –12#0 $J mol –1

. A data boo$ value for the same reaction is ∆ H c  3 –2:0 $J mol –1

.

+i, -uggest one reason why the eperimental value is very different from the data

 boo$ value.

...........................................................................................................................

+ii, !his data boo$ value of ∆ H c  for butanone +–2:0 $J mol –1

, refers to the

formation of carbon dioide gas and water in the gaseous state. (ow would this

value differ if it referred to the formation of water in the li*uid stateE 6plain your

answer.

 Difference .........................................................................................................

 Explanation ......................................................................................................

...........................................................................................................................(3)

 

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+d, Calculate a value for the standard enthalpy of formation for li*uid ethanethiol&C2(>-(.

5se the e*uation given below and enthalpy of combustion data from the following table.

-ubstance C2(>-(+l, C+s, (2+g, -+s,

∆ H c  / $J mol –1  –110 –:# –2"' –2#

2C+s, :(2+g, -+s, →  C2(>-(+l,

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

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(Total 12 marks)

9. +a, @efine the term standard enthalpy of formation.

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................(3)

+b, %rite an e*uation& including state symbols& for a reaction for which the enthalpy change

is the standard enthalpy of formation of li*uid C(: 8)2

...................................................................................................................................(2)

+c, Five the name of the principle or law which enables enthalpies of formation to be

calculated from enthalpies of combustion.

.....................................................................................................................................(1)

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+d, Bn the presence of a catalyst& gaseous hydrogen cyanide& (C8& burns in an ecess of

oygen as shown by the e*uation below.

(C8+g, 20

1 )2+g, → 2

1 (2)+g, C)2+g, 8)2+g,

-ome standard enthalpies of combustion&∆ H   are given in the table below.

-ubstance (C8+g, (2+g, C+s, 82+g,

∆ H  /$J mol –1  –'11 –22 –:# '"

5se these data to calculate a value for the standard enthalpy of formation for gaseous

hydrogen cyanide.

...................................................................................................................................

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(Total 10 marks)

10. +a, -tate what is meant by the term mean bond enthalpy.

...............................................................................................................................

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+b, 6thanal has the structure

(

C C(

( (

)

Faseous ethanal burns as shown by the e*uation

C(:C()+g, 2G)2+g, →  2(2)+g, 2C)2+g,

5se the mean bond enthalpy data given below to answer the following *uestions.

7ond 9ean bond enthalpy/$J mol –1

CH( 1:

CHC :

C33) :'

)33) #"

)H( '

 

+i, Calculate the enthalpy change which occurs when all the bonds in the reactants

shown in the above e*uation are bro$en.

......................................................................................................................

......................................................................................................................

......................................................................................................................

......................................................................................................................

+ii, Calculate the enthalpy change which occurs when all the bonds in the products

shown in the above e*uation are formed.

......................................................................................................................

......................................................................................................................

......................................................................................................................

+iii, (ence& calculate the enthalpy change for the complete combustion of ethanal as

shown in the e*uation above.

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(Total 7 marks)

 

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11. +a, @efine the term standard molar enthalpy of formation& ∆ H f  .

...............................................................................................................................

...............................................................................................................................

...............................................................................................................................(3)

+b, -tate (esss law.

...............................................................................................................................

...............................................................................................................................(1)

+c, Iropanone& C(:C)C(:& burns in oygen as shown by the e*uation

C(:C)C(:+l, )2+g, →  :(2)+l, :C)2+g,

5se the data given below to calculate the standard enthalpy of combustion of propanone.

C)2+g, (2)+l, C(:C)C(:+l,

∆ H f  /$J mol –1  –:# –2"' –2"

...............................................................................................................................

...............................................................................................................................

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...............................................................................................................................(3)

(Total 7 marks)

 

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12.  8itrogen& hydrogen and oygen undergo the reactions shown below.

Reaction 12

1 82+g,

2

1)2+g, 8)+g,   ∆ H   3 #1 $J mol

 –1

Reaction 22

1 82+g, 1

2

1 (2+g, 8(:+g,   ∆ H   3 –' $J mol

 –1

Reaction 3 (2+g, 2

1 )2+g, (2)+g,   ∆ H   3 –22 $ mol –1

5se this information in answering the *uestions that follow.

+a, %hat name is given to the symbol ∆ H  E 6plain fully what it means.

 Name. ..............................................................................................................

 Explanation. ....................................................................................................

..........................................................................................................................

..........................................................................................................................(4)

+b, +i, %rite an e*uation for the reaction of nitrogen monoide& 8)& with hydrogen to

form ammonia and steam.

..........................................................................................................................

..........................................................................................................................

+ii, Calculate the value of∆ H   for this reaction& using the data given at the beginningof uestion :.

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................

..........................................................................................................................(4)

(Total 8 marks)

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+c, +i, -tate what is meant by the term mean bond enthalpy.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

+ii, 5sing the standard enthalpy of formation of methane given in part +b, and the data

given below& calculate the mean bond enthalpy of the C;H bond in methane.

C+s, → C+g,   ∆ H   3 1> $J mol –1

(2+g, → 2(+g,   ∆ H   3 :' $J mol –1

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

+iii, 5sing the C–( bond enthalpy calculated in part +c,+ii, and the standard enthalpy

change for the reaction given below& calculate the mean bond enthalpy of the C–C

 bond in propane.

 8.7. Bf you failed to complete part +c,+ii,& you may assume that the mean bondenthalpy of the C–( bond is :#0 $J mol

 –1. +!his is not the correct value.,

( C C C ( + g ,

( ( (

( ( (

: C + g , " ( + g , 3 0 2 0 $ J m o l∆  H  – 1  

...........................................................................................................................

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...........................................................................................................................(7)

(Total 13 marks)

 

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15. +a, @efine the term standard enthalpy of combustion& ∆ H  .

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

+b, 9ethanethiol& C(:-(& is added to natural gas in order to give it a smell. %hen

methanethiol burns in air it forms carbon dioide& water and sulphur dioide. %rite a

 balanced e*uation for this combustion reaction.

.....................................................................................................................................(1)

+c, A value for the enthalpy of formation of methanethiol can be determined using (essLs

aw and enthalpies of combustion. Bn this calculation& which three enthalpy values

would be needed in addition to the enthalpy of combustion of methanethiolE

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

+d, Carbon disulphide& C-2& burns in air as followsM

C-2+l, :)2+g, → C)2+g, 2-)2+g,

-ome standard enthalpies of formation& ∆ H   are given in the table below.

-ubstance C-2+l, C)2+g, -)2+g,

∆ H  /$J mol –1 "" –:# –2#

 

5se these data to calculate a value for the enthalpy of combustion of li*uid carbon

disulphide.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

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(Total 9 marks)

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16. !he tables below contain values of standard enthalpy of combustion& ∆ H   and standard

enthalpy of formation& ∆ H  .

C + g r a p h i t e , - + s ,

∆  H    / $ J m o l  – 1c

∆  H    / $ J m o l  – 1f 

 – : # – 2 #

2C - + l , 8 ) + g , C ) + g , 2- ) + g ,

" " # 0 – 1 1 1 – 2 #

 

+a, -tate (esss aw.

....................................................................................................................................

....................................................................................................................................(2)

+b, 6plain the meaning of the term standard enthalpy of combustion of a compound.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(3)

+c, +i, %rite e*uations& with state symbols& for the formation of li*uid carbon disulphide+C-2, from its elements and for the combustion of carbon disulphide to form

carbon dioide and sulphur dioide.

 Euation for formation of !S 2

............................................................................................................................

 Euation for combustion of !S 2

............................................................................................................................

+ii, Calculate the enthalpy of combustion of carbon disulphide& using its enthalpy offormation and the enthalpies of combustion from the tables on above.

............................................................................................................................

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+d, Carbon disulphide reacts eplosively with nitrogen monoide +8), according to the

following e*uation.

C-2+l, >8)+g, → C)+g, 2-)2+g, 2

> 82+g,

5se the enthalpies of formation given in the table to calculate the enthalpy change in this

reaction.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

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....................................................................................................................................(3)

(Total 13 marks)

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17. !he structure of hydra4ine can be represented as shown below.

 8 8

((

((  

+a, +i, %rite an e*uation for the formation of hydra4ine from its elements.

............................................................................................................................

+ii, -team and nitrogen gas are the combustion products of gaseous hydra4ine.

%rite an e*uation for this reaction.

............................................................................................................................

+iii, 5se the data given below to calculate the standard enthalpy of formation of

gaseous hydra4ine.

∆ H   82(+g, 3 –>'" $J mol –1

∆ H   (2)+g, 3 –22 $J mol –1

............................................................................................................................

............................................................................................................................

............................................................................................................................

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............................................................................................................................(4)

+b, -tate what is meant by the term mean bond enthalpy.

....................................................................................................................................

....................................................................................................................................(2)

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+c, 5se the enthalpy of formation of hydra4ine calculated in part +a, and the mean bond

enthalpies given below to calculate the enthalpy of the bond between the two nitrogen

atoms in hydra4ine.

 87 Bf you failed to complete part +a, you may assume that

∆( 82(+g, 3 >0 $J mol –1

 +not the correct value,.

7ond 8–(  8≡ 8 (–(

9ean bond enthalpy/$J mol –1 :"# #> :'

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(3)

+d, !he measured 8;8 bond enthalpy in hydra4ine is 1>" $J mol –1

. 6plain why the bond

enthalpy when calculated correctly in part +c, does not agree with the measured value.

....................................................................................................................................

....................................................................................................................................(1)

(Total 10 marks)

18. !he table below gives some standard enthalpies of formation& ∆ H  .

-ubstance C2('+g, D2+g, CD+g, (D+g,

∆ H   /$J mol –1  –"> 0 –'"0 –2'#

+a, @efine the term standard enthalpy of formation.

.....................................................................................................................................

.....................................................................................................................................

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+b, %hy is the value for the standard enthalpy of formation for fluorine e*ual to 4eroE

.....................................................................................................................................(1)

+c, Calculate the standard enthalpy change for the following reaction.

C2('+g, D2+g, 2CD+g, '(D+g,

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

+d, !he table below shows some bond enthalpies.

7ond C–C C–( D–D

7ond enthalpy /$J mol–1 :" 12 1>"

+i, %hy are the values for C–C and C––( described as mean bond enthalpiesE

............................................................................................................................

............................................................................................................................

+ii, -uggest the most li$ely first step in the reaction shown in part +c, and give a reason

for your answer.

 "irst step in the reaction ....................................................................................

 #eason ...............................................................................................................(4)

(Total 11 marks)

19. +a, @efine the terms standard enthalpy of formation and standard enthalpy of combustion.

Standard enthalpy of formation..................................................................................

.....................................................................................................................................

.....................................................................................................................................

Standard enthalpy of combustion................................................................................

.....................................................................................................................................

.....................................................................................................................................(6)

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+b, 5se the standard enthalpies of formation& ∆ H  & given below

Compound ∆ H   / $J mol –1

C)2+g, –:#

C:()(+l, –:0

(2)+l, –2"'

to calculate the standard enthalpy of combustion of an alcohol C:()(& as shown by the

e*uationM

C:()(+l, G)2+g, → :C)2+g, (2)+l,

.....................................................................................................................................

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+c, A value for the enthalpy of combustion of the alcohol C:()( was determined in the

laboratory using the apparatus shown below. !he following results were obtained.

t h e r m o m e t e r

c o p p e r c a l o r i m e t e r

w a t e r

 b u r n e r

9ass of water in the calorimeter 3 200 g

Bnitial temperature of water 3 1> NC

Dinal temperature 3 :0 NC

9ass of alcohol burned 3 0.#0 g

+i, Calculate the heat energy re*uired to raise the temperature of the water from

1> C to :0 C. !he specific heat capacity of water is .2 J g –1

 K  –1

.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

+ii, Calculate the number of moles of the alcohol& C:()(& burned.

...........................................................................................................................

...........................................................................................................................

+iii, (ence& calculate a value for the enthalpy of combustion of 1.0 mol of the alcohol.

...........................................................................................................................

...........................................................................................................................

+iv, Five to reasons why you would epect your answer to part +c,+iii, to differ from

that in part +b,.

 #eason 1 ...........................................................................................................

...........................................................................................................................

 #eason 2 ...........................................................................................................

...........................................................................................................................(8)

(Total 17 marks)

 

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20. An e*uation for the combustion of cyclopropane& C:('& is shown below.

C:('+g, 2

1 )2+g, → :C)2+g, :(2)+g,

!he standard enthalpy of combustion of cyclopropane can be calculated either from standard

enthalpies of formation or by using mean bond enthalpies.

+a, 5se the standard enthalpies of formation given below to calculate the standard enthalpy

of combustion of cyclopropane.

∆ H   C:('+g, 3 >: $J mol –1

∆ H   C)2+g, 3 –:#: $J mol –1

∆ H   (2)+g, 3 –22 $J mol –1

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+b, -tate what is meant by the term mean bond enthalpy.

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+c, !he following mean bond enthalpies have been obtained from a data boo$. 5se these

values to calculate the standard enthalpy of combustion of cyclopropane.

C–C : $J mol –1

C–( 1: $J mol –1

C3) "0> $J mol –1

)3) #" $J mol –1

)–( ' $J mol –1

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8/17/2019 2.1 Energetics Database (1)

http://slidepdf.com/reader/full/21-energetics-database-1 23/23

 

+d, 6plain& by reference to the structure of cyclopropane& why the enthalpy of combustion

calculated in part +a, is more eothermic than that calculated in part +c,.

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(Total 10 marks)