ChemEquations

Lab LR/TY Stoichi-ometry

Potpourri

100 100 100 100 100

200 200 200 200 200

300 300 300 300 300

400 400 400 400 400

500 500 500 500 500

Final

100 Chem Eqns

How is bromine written in a chemical equation?

Answer

Chem Eqns 100

Br2

It is diatomic

200 Chem Eqns

Write a balanced equation, with phases, for the formation of carbon monoxide from its

elements.Answer

Chem Eqns 200

2C(s) + O2(g) 2CO(g)

300 Chem Eqns To balance a chemical equation, you may change _______ but you may

not change ______Answer

Chem Eqns 300

To balance a chemical equation, you may change _coefficients_ but may not

change _subscripts or formulas_

400 Chem Eqns

Write a balanced chemical equation for the combustion of heptane, C7H16

AnswerAll Play!!!

Chem Eqns 400 Answer

1C7H16 + 11O2 7CO2 + 8H2O

500 Chem Eqns

Write the balanced equation, with phases, for the reaction between silver nitrate and copper.

Answer All Play!!!!

Chem Eqns 500 Answer

2AgNO3(aq) + Cu(s) 2 Ag(s) + Cu(NO3)2(aq)

100 LabWhat observation allows you to determine that a reactant is the

Limiting Reactant?

Answer

Lab100 Answer

It is gone – used up. It may not always be

possible to observe this, for instance if it is in the

aqueous phase.

200 LabWhat observation allows you to determine that a reactant is the Excess Reactant?

What is the Excess Reactant in most combustions? Explain.

Answer

Lab 200 Answer

• Some of the excess reactant is left over after the reaction stops.

• Oxygen is the ER in combustions b/c it comes from the air and is unlimited.

300 LabExplain why a candle loses mass as it burns.

Answer

Lab 300 Answer

Products are CO2 and H2O gases that escape

into the air during combustion

400 LabIn the AgNO3 Lab, which of the following experimental errors would give a ratio of 1.10 mol Ag/1mol AgNO3?A. Running more than 30 min.B. Insufficient washing/decantingC. Weighing Ag while it is still wet.D. Impure reactants

Answer All Play!!

Lab 400 Answer

• B and C will increase mass of Ag

insufficient washing leaves some copper nitrate in with Ag. Weighing wet gives mass of Ag + water• A does not have an effect b/c the reaction

STOPS when limiting reactant is used up. More time does not give more product after LR is gone.

• D decreases mass of product

500 Lab

What was the purpose of washing and decanting the silver after the

silver nitrate reaction had finished?

Answer

Lab 500 Answer

To purify the Ag by rinsing away the water soluble product, Cu(NO3)2.

100 LR/TY

What is the molar mass, to 2 decimals, of Cu(NO2)2?

Answer

All Play!

LR/TY 100 Answer

155.57 g/mol

200 LR/TY

• Write the mole ratio of phosphorus to fluorine in the following equation

P4 + 6F2 4PF3

Answer

All Play!!!

LR/TY 200

1mole P4 6mol F2

300 LR/TYStoichiometry predicts 2.55 g of Ag product. Data gives the

following: empty beaker = 45.68 g

beaker plus Ag = 47.68 gWhat is % Yield?

Answer

All Play!!!

LR/TY 300 Answer

% Yield = 2.00g x 100

2.55 g

= 78.4%

400 LR/TYList 4 reasons, other than human error, why yield is usually less than 100%.

All Play!!Answer

LR/TY 400 Answer

See your class notes!

500 LR/TYIf 5.00 g of S8 and 10.00 g of Cu are

combined, what is the theoretical yield of product?

16Cu + S8 8Cu2S

AnswerAll Play!!

LR/TY 500 Answer

5.00 g of S8 gives 0.155910 mol Cu2S

10.00 g of Cu gives 0.078678 mol Cu2S

Cu is the Limiting Reactant

0.078678 mol Cu2S x 159.17g/mol =

12.52 g Cu2S

100 Stoichiometry

What two types of conversion factors are needed for

stoichiometry calculations?Answer

Stoichiometry 100 Answer

•Mole Ratio from the balanced equation

•Molar Mass

200 Stoichiometry

What part of a balanced equation gives the numerical

part of the mole ratio?Answer

All Play!!

Stoichiometry 200 Answer

Coefficients

300 Stoichiometry

S + 3F2 SF6

What mass of fluorine produces 0.75

moles of SF6?

Answer

All Play!!

Stoichiometry 300 Answer

S + 3F2 SF6

?g F2 = 0.75 mol SF6 x 3molF2 x 38.00 g F2

1 1mol SF6 1mol F2

= 85.5 A 86 g F2

400 Stoichiometry

S + 3F2 SF6

What mass of sulfur reacts with 3.80 g of Fluorine?

Answer

ALL PLAY!

Stoichiometry 400 AnswerS + 3F2 SF6

?g S = 3.80g F2 x 1mol F2 x 1mol S x 32.07gS

1 38.00g F2 3molF2 1mol S

=1.07 g S

S + 3F2 SF6

What is the theoretical yield of SF6 when 3.00 mol of F2 reacts

with excess sulfur? Answer

500 StoichiometryAll Play!!

Stoichiometry 500 AnswerS + 3F2 SF6

? g SF6 = 3.00mol F2 x 1molSF6 x 146.07g SF6

1 3mol F2 1mol SF6

= 146 g SF6

100 Potpourri

A balanced equation has the same number

of ______ on both sides of the arrow.

Answer

Potpourri 100

A balanced equation has the same number of each type of atoms on both sides of

the arrow.

200 Potpourri

The maximum amount of product possible in a chemical

reaction is ________.

Answer

All Play!!

Answers for Potpourri 200

The maximum amount of product possible in a chemical reaction is

theoretical yield.

300 Potpourri

• How many questions must King Arthur and his Knights each answer in order to cross the Bridge of Death and keep from being cast into the Gorge of Eternal Peril?All Play! Answer

Potpourri 300 Answer

Three (3) (III)

400 PotpourriExplain why the product of burning Iron weighs more than the reactant Iron (steel wool)

Answer

Potpourri 400 Answer

Only one reactant, Fe, is weighed. O2 cannot be weighed.

After reaction, Fe atoms are bonded to Oxygen atoms from

the air, so you are weighing both Fe and O

500 Potpourri

Balance and add phase scripts to the following equation.

Fe2O3 + CO Fe + CO2

AnswerAll Play!!

Potpourri 500 Answer

1Fe2O3(s) + 3CO(g) 2Fe(s) + 3 CO2(g)

Final Jeopardy

Why would a company be interested in the % Yield of its

chemical reactions?Answer

Final Jeopardy Answer

To evaluate cost effectiveness