CHAPTER 7 : ACID AND BASE

SECTION A: Common Mistake Made By The Candidates

Common mistakes (Acids & Bases)

Hydrogen ions, H

+

, and hydroxonium ions, H3

O

+

, are not the same.

Hydrogen ions, H

+

, and hydroxonium ions, H3

O

+

, are similar. They enable acidic solutions to

show acidic properties.

All bases contain the hydroxide ion, OH

-

Not all bases contain the hydroxide ion, OH

-

. For example, sodium oxide, Na2

O does not

hydroxide ions.

A base and an alkali are similar.

An alkali are bases but not all bases are alkalis. Soluble bases dissolve in water to form

alkalis.

Dry ethanoic acid, CH3

COOH, shows acidic properties.

Dry ethanoic acid, CH3

COOH, does not show acidic properties. Dry ethanoic acid,

CH3

COOH, exists as molecules.

The higher the molarity of an acid, the higher is the pH value.

The higher the molarity of an acid, the lower is the pH value.

An acid with high molarity must be a strong acid.

An acid with high molarity not necessarily is a strong acid. For example, 10 mol dm

-3

of

ethanoic acid, is a weak acid.

Mole and molarity are the same.

1 | P a g e A c i d a n d B a s e s

X

√

X

√

X

√

X

√

X

√

X

√

X

A mole is a unit for the amount of matter. The molarity is the number of moles of the solute in

1 dm

3

of its solution.

The titration between an acidic solution and any base, such as solid copper(II) hydroxide,

Cu(OH)2

, can be done.

Titration method can only be carried out between acidic solutions and alkaline solutions.

SECTION B: DIAGNOSTIC QUESTIONS

a) Objective Questions

1. Which of the following is true of a weak alkali? Antara berikut yang manakah benar mengenai alkali lemah? A Unable to neutralise acid Tidak boleh meneutralkan acidB The pH value is less than 7 Nilai pH kurang daripada 7C Able to change blue litmus paper to red Boleh menukarkan kertas litmus biru ke merahD Ionises partially in water to produce hydroxide ion Mengion separa dalam air untuk menghasilkan ion hidroksida

2 Which of the following information is true about an alkali? Antara maklumat berikut yang manakah benar tentang alkali?

A Not corrosive Tidak mengkakis B An alkali is a soluble base Alkali ialah bes yang larut

B Acid reacts with alkali to produce salt and hydrogen gas. Asid bertindakbalas dengan alkali meng- hasilkan garam dan gas hydrogen.C Acid reacts with metal oxide to produce salt, water and hydrogen gas. Asid bertindakbalas dengan oksida logam menghasilkan garam,air dan gas hydrogen.D Acid reacts with carbonate of metal to produce salt, water and carbon dioxide gas. Asid bertindakbalas dengan karbonat logam menghasilkan garam, air dan gas karbon dioksida.

4. Which of the following substance is acidic? Antara bahan berikut yang manakah bersifat asid?

A Lithium okside B Ammonia Litium oksida Ammonia C Sodium hydroxide D Carbon dioxide Natrium hidroksida Karbon dioksida

5. Which of the following statement correctly describes a strong alkali? Antara pernyataan berikut, yang manakah

2 | P a g e A c i d a n d B a s e s

√

X

√

C A strong alkali has a low pH value Alkali kuat mempunyai nilai pH yang rendah D A weak alkali has a high degree of ionisation Alkali lemah mempunyai darjah pengionan yang tinggi

3 Which of the following chemical property of an acid is true? Antara berikut yang manakah benar mengenai sifat kimia asid?

A Acid reacts with metal to produce salt and water. Asid bertindakbalas dengan logam meng- hasilkan garam dan air.

menerangkan tentang alkali kuat dengan betul?

I Has a low pH value Nilai pH yang rendah II Ionises completely in water Mengion dengan lengkap dalam air III Has a high concentration of hydroxide ions Mempunyai kepekatan ion hidroksida yang tinggi IV Exist as molecules in water Wujud sebagai molekul dalam air

A I and II B I and IV I dan II I dan 1VC II and III D III and IV II dan III III dan IV

6. Below is the information of the two solutions: Maklumat mengenai dua larutan adalah seperti dibawah:

Which of the following statement are true base on the information. Berdasarkan maklumat di atas pilih pernyataan yang benar.

I Ammonium hydroxide solution is a weak alkali while sodium hydroxide solution is a strong alkali. Larutan ammonium hidroksida adalah alkali adalah lemah manakala arutan natrium hidroksida adalah alkali kuat.II The pH value of sodium hydroxide solution is higher than the pH value of ammonium hydroxide solution. Larutan natrium hidroksida mempunyai nilai pH yang lebih tinggi berbanding

A I and III B III and IV I dan III III dan IVC I, II and III D I, II, III and IV I,II dan III I, II, III dan IV

7 Which of the following facts is matched correctly? Antara fakta berikut yang manakah dipadamkan dengan betul?

Acid formula / formula asid

Types of acid / Jenis asid

Basicity of acid / kebesan asid

A CH3COOHWeak acid/ asid lemah

4

B HClWeak acid/ asid lemah

1

C H2SO4

Strong acid / asid kuat

2

D H2CO3

Strong acid / asid kuat

2

8 Which solution shows the lowest pH value? Larutan manakah menunjukkan nilai pH terendah?

3 | P a g e A c i d a n d B a s e s

0.5 mol dm-3 sodium hydroxide solution pH=13 0.5 mol dm-3 larutan natrium hidroksida

0.5 mol dm-3 ammonium hydroxide solution pH= 9 0.5 mol dm-3 larutan ammonium hidroksida

larutan ammonium hidroksida.III The degree of dissociation of sodium hydroxide solution in water is higher than the degree of dissociation of ammonium hydroxide solution in water. Darjah penceraian larutan natrium hidroksida dalam air adalah lebih tinggi berbanding darjah penceraian larutan ammonium hidroksida dalam air.IV The concentration of OH- ion in sodium hydroxide solution is higher than in ammonium hydroxide solution. Larutan natrium hidroksida mempunyai kepekatan ion OH- yang lebih tinggi daripada larutan ammonium hidroksida.

A 0.5 mol dm-3 sulphuric acid 0.5 mol dm-3 acid sulfurik B 0.5 mol dm-3 ethanoic acid 0.5 mol dm-3 asid nitrik C 0.5 mol dm-3 aqueous ammonia 0.5 mol dm-3 ammonia akueous D 0.5 mol dm-3 sodium hydroxide solution 0.5 mol dm-3 larutan natrium hidroksida

9 The equation shows the reaction between sulphuric acid and potassium hydroxide. Persamaan menunjukkan tindakbalas di antara asid sulfurik dan kalium hidroksida.

H2SO4 + 2KOH K2SO4 + 2H2O

What is the volume of 1.0 mol dm-3 potassium hydroxide solution which can neutralises 25.0 cm3 of 1.0 mol dm-3

sulphuric acid? Berapakah isipadu 1.0 mol dm-3 larutan kalium hidroksida yang boleh meneutralkan 25.0 cm3 asid sulfurik 1.0 mol dm-3? A 12.5 cm3 B 25.0 cm3

C 50.0 cm3 D 75.0 cm3

10 Below are the properties of an acid. Berikut adalah beberapa sifat suatu asid. -Show a pH value of 1-Menunjukkan nilai pH 1-12.5 cm3 0.1 mol dm-3 of this acid neutralises 25.0 cm3 0.1 mol dm-3 KOH-12.50 cm3 0.1 mol dm-3 larutan asid ini telah meneutralkan 25.0 cm3 0.1 mol dm-3 KOH

Which of the following best describe to identify of this acid.Antara berikut yang manakah paling sesuai bagi menjelaskan identiti asid ini. A 0.1 mol dm-3 of ethanoic acid. 0.1 mol dm-3 asid etanoik. B 0.1 mol dm-3 of hydrochloric acid. 0.1 mol dm-3 asid hidroklorik.C 0.1 mol dm-3 of sulphuric acid 0.1 mol dm-3 asid sulfurik D 0.1 mol dm-3 of nictric acid

0.1 mol dm-3 asid nitrik

4 | P a g e A c i d a n d B a s e s

b) Subjective Questions

1 The table shows a several acids. Jadual dibawah menunjukkan beberapa asid.

Sulphuric acid, H2SO4, Carbonic acid, H2CO3, Hydrochloric acid, HCl, Nitric acid, HNO3, Ethanoic acid, CH3COOH

Asid sulfurik, H2SO4, Asid karbonik, H2CO3, Asid hidroklorik, HCl, Asid nitric, HNO3, Asid etanoik, CH3COOH

(a) Classified the acids into strong acids and weak acids: Kelaskan asid mengikut asid kuat dan asid lemah.

Strong acidAsid kuat

Weak acidAsid lemah

(b) Classified the acids into monoprotic acids and diprotic acids: Kelaskan asid mengikut asid monobes dan asid dwibes .

Monoprotic acidAsid monobes

Diprotic acidAsid dwibes

5 | P a g e A c i d a n d B a s e s

2 The table shows a several alkalis. Jadual dibawah menunjukkan beberapa alkali.

Ammonia solution, NH3 , Potassium hydroxide, KOH , Barium hydroxide, Ba(OH)2 , Calcium hydroxide, Ca(OH)2.

Larutan ammonia, NH3 ,Kalium hidroksida, KOH , Barium hidroksida, Ba(OH)2 Kalsium hidroksida, Ca(OH)2.

Classified the alkalis into strong alkalis and weak alkalis: Kelaskan alkali mengikut:

Strong alkali Alkali kuat

Weak alkaliAlkali lemah

3 An acid-base indicator is used to detect the end point of titration when it changes colour. Penunjuk asid-bes digunakan untuk mengesan takat akhir titratan apabila warnanya berubah.

(a) Name two indicators which commonly used in acid-base titration. Namakan dua penunjuk yang biasa digunakan dalam titratan asid-bes.

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

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

(b) Based on your answers at 3(a), state the colour changes for each indicator stated. Berdasarkan jawapan anda pada 3(a), nyatakan perubahan warna bagi setiap penunjuk

dinyatakan.

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

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

4 Diagram shows the ionisation that happen on hydrogen chloride in water.Rajah menunjukkan pengionan yang berlaku ke atas hydrogen klorida dalam air.

6 | P a g e A c i d a n d B a s e s

Chloride ion/ ion klorida, Cl-

hydrogen ion/ ion hidrogen,H+

Based on diagram, state two information about hydrogen chloride in water.Berdasarkan rajah, nyatakan dua maklumat tentang hidrogen klorida dalam air.

(1): ……………………………………………………………………………………………….

(2) ………………………………………………………………………………………………

5 Diagram shows the particles in aqueous ammonia solution.Rajah menunjukkan zarah-zarah dalam larutan akueous ammonia.

Based on diagram, explain why most of ammonia molecules still exist in the solution.Berdasarkan rajah, terangkan mengapa kebanyakan molekul ammonia masih terdapat dalam

larutan.

…………………………………………………………………………………………………...

…………………………………………………………………………………………………...

6

(a) Give the relationship between moles(n) of HCl, volume(V) of HCl and molarity(M) of HCl.

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

(b) Calculate the number of moles of hydrochloric acid, HCl in each solution.

7 | P a g e A c i d a n d B a s e s

Ammonium ion/ ion ammonium

hydroxide ion/ ion hidroksida

Ammonia molecule/ molekul ammonia

Solution A: 50 cm3 of 1.0 mol dm-3 hidrochloric acid, HClSolution B: 10 cm3 of 2.0 mol dm-3 hidrochloric acid, HCl

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

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

(c) Calculate the volume of solution A needed to prepare 50 cm3 of 0.3 mol dm-3 hidrochloric acid, HCl.

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

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

(d) Complete the reaction below:

HCl + Ba(OH)2 →

(e) What is the volume of 0.2 mol dm-3 barium hydroxide, Ba(OH)2 solution needed to neutralise solution B.

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

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

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

8 | P a g e A c i d a n d B a s e s

SECTION C: PAPER 2

a) Structure Question

1 Dry ammonia gas requires water to exhibit some of its properties.Diagram 1 shows Set I and Set II for an experiment carried out to study the properties of ammonia in water and ammonia in propanone.Gas ammonia kering memerlukan air untuk menunjukkan beberapa sifat-sifatnya.Rajah 1 menunjukkan Set I dan Set II bagi eksperimen yang dijalankan untuk mengkaji sifat-sifat ammonia dalam air dan dalam propanon.

Set I Set II

Diagram 1Rajah 1

The two solutions in Set I and Set II are tested with red and blue litmus paper.Kedua-dua larutan dalam Set I dan Set II diuji dengan kertas litmus merah dan biru.

(a) (i) What is the function of litmus paper in this test?. Apakah fungsi kertas litmus dalam ujian ini?.

……………………………………………………………………………………...[1 mark]

(ii) In Table 1, record the colour changes of litmus paper for Set I and Set II. Dalam Jadual 1, rekodkan perubahan warna kertas litmus bagi Set I dan Set II.

[2 marks]SolutionLarutan

Set I Set II

Red litmus

9 | P a g e A c i d a n d B a s e s

Ammonia in waterAmmonia dalam air

Ammonia in propanoneAmmonia dalam propanon

Litmus paper Kertas litmus

Litmus paperKertas litmus

paperKertas litmus merah

…………………

…………………

……………….

……………….Blue litmus paperKertas litmus biru

…………………

…………………

………………..

……………….. Table 1

(iii) Explain why the observations in both Set I and II are different. Terangkan mengapa pemerhatian dalam kedua-dua Set I dan II berbeza.

…………………………………………………………………………………….

…………………………………………………………………………………….

…………………………………………………………………………………….[2 marks]

(b) Name the type of particles exist in ammonia solution forNamakan jenis zarah wujud dalam larutan ammonia bagi

(i) Set I : ………………………………………… [ 1 mark] (ii) Set II : ………………………………………… [ 1 mark]

(c) Draw a label diagram the set-up of apparatus for preparation of ammonia solution in water or in propanone . Lukiskan gambar rajah berlabel susunan radas bagi penyedian larutan ammonia dalam air atau propanon.

[2 marks](d) Name one another substance that can be replaces propanone in Set II.

Namakan satu bahan lain yang dapat menggantikan propanon dalam Set II.

…………………………………………………………………………………………...[1 mark]

10 | P a g e A c i d a n d B a s e s

b) Essay Question

1 (a) Hydrogen chloride is a neutral gas and dissolves in water to form an acidic solution. Hidrogen klorida adalah gas neutral dan larut dalam air membentuk larutan berasid.

Explain why dry hydrogen gas is neutral while aqueous hydrogen chloride is acidic. Terangkan mengapa gas hidrogen klorida adalah neutral manakala hidrogen klorida akueous adalah berasid.

[3 marks](b) Explain how potassium carbonate can be used to identify that an aqueous solution

contains an acid. Terangkan bagaimana kalium karbonat dapat digunakan untuk menentusahkan satu larutan akueous itu mengandungi asid.

[1 mark](c) (i) Stomach pain due to excess acid can be treated using anti-acids.

Name the active ingredients contain in the anti-acid and explain how the excess acid in the stomach can be reduced. Sakit perut disebabkan lebihan asid dapat dirawat menggunakan ubat antasid. Namakan bahan aktif yang terdapat dalam ubat antasid dan terangkan bagaimana

lebihan asid dalam perut dapat dikurangkan.

(ii) Sulphur dioxide which emitted by industries factory can causes environmental pollution.

State a method how to treat this gas before discharged to environment. Sulfur dioksida yang dibebaskan oleh kilang industri boleh menyebabkan

pencemaran alam sekitar.Nyatakan satu kaedah bagaimana merawat gas ini sebelum ia dilepaskan ke

sekeliling.[6 marks]

(d) Baking powder can be used to cure bee stings and vinegar can be used to cure wasp stings. Based on the statement above, give your explanation. Serbuk penaik dapat digunakan untuk merawat sengatan lebah dan cuka dapat digunakan

untuk merawat sengatan tebuan. Berdasarkan penyataan di atas, berikan penjelasan anda.

[6 marks](e) Table 1 shows some information about acid X and acid Y.

Jadual 1 menunjukkan beberapa maklumat tentang asid X dan asid Y.

Acidasid X Y

11 | P a g e A c i d a n d B a s e s

Concentration/ mol dm-3

Kepekatan/ mol dm-30.5 0.5

pH 3.5 1.0

Table 1Jadual 1

Based on data in Table 1, compare the strength of acid X and acid Y.Explain your answer based on degree of ionisation of acid in water.Berdasarkan data dalam Jadual 1, bandingkan kekuatan asid X dan asid Y.Jelaskan jawapan anda berdasarkan darjah pengionan asid dalam air.

[4 marks]

12 | P a g e A c i d a n d B a s e s

SECTION D: PAPER 3

Structure questions

1 An experiment is carried out to determine the concentration of nitric acid. During the experiment, 25.0 cm3 of 0.10 mol dm-3 sodium hydroxide solution which contains phenolphthalein is titrated with nitric acid from a burette. Diagram 1.1 shows the initial and final readings of three titrations that are carried out.Satu eksperimen telah dijalankan untuk menentukan kepekatan asid nitric. Sepanjang eksperimen, 25.0 cm3 larutan natrium hidroksida 0.10 mol dm-3 yang mengandungi fenoftalein telah dititratkan dengan asid nitrik dari sebuah buret.Rajah 1.1 menunjukkan bacaan awal dan akhir bagi tiga titratan yang dijalankan.

The equation shows the reaction between nitric acid and sodium hydroxide solution.Persamaan menunjukkan tindak balas antara asid nitrik dan larutan natrium hidroksida.

HNO3 + NaOH → NaNO3 + H2O

Initial Final Initial Final Initial Final reading reading reading reading reading reading bacaan bacaan bacaan bacaan bacaan bacaan awal akhir awal akhir awal akhir

Titration I Titration II Titration III Titratan I Titratan II Titratan III

Diagram 1.1 Rajah 1.1

(a) Complete Table 1.1 by recording the readings for each of the titrations and the volume of nitric acid used.

13 | P a g e A c i d a n d B a s e s

2

3

27

28

16

17

41

42

11

12

36

Lengkapkan Jadual 1.1 dengan merekod bacaan bagi setiap titratan dan isipadu asid nitrik yang digunakan.

Titration I II III

Final burette reading

Bacaan akhir buret/cm

3

Initial burette reading

Bacaan awal buret/ cm

3

Volume of nitric acid used

Isipadu asid nitric yang digunakan/ cm

3

Table 1.1Jadual 1.1

[3 marks]

(b) Draw a labelled diagram for the set-up of apparatus for this experiment. Lukiskan gambar rajah berlabel susunan radas bagi eksperimen ini.

[3 marks] (c) State one hypothesis based on this experiment.

……………………………………………………………………………………………………...

……………………………………………………………………………………………………...[3 marks]

14 | P a g e A c i d a n d B a s e s

(d) For this experiment, state: Bagi eksperimen ini, nyatakan:

(i) The manipulated variable Pembolehubah dimanipulasikan

………………………………………………………………………………………………

(ii) The responding variable Pembolehubah bergerak balas

………………………………………………………………………………………………

(iii) The constant variable Pembolehubah dimalarkan

……………………………………………………………………………………………...[3 marks]

(e) Phenolphthalein is used as an indicator for this experiment. Diagram 1.2 shows the colour and pH values of sodium hydroxide solution and sodium nitrate solution before and after the end point are achieved. Fenolfthalein digunakan sebagai penunjuk dalam eksperimen ini. Rajah 1.2 menunjukkan warna dan nilai pH larutan natrium hidroksida dan larutan natrium nitrat sebelum dan selepas takat akhir dicapai.

Diagram 1.2 Rajah 1.2

(i) Referring to Diagram 2.2, state two observations based on this experiment. Merujuk kepada Diagram 2.2, nyatakan dua pemerhatian berdasarkan

eksperimen ini.

Observation I: …………………………………………………………………………...

Observation II: …………………………………………………………………………..

15 | P a g e A c i d a n d B a s e s

Sodium hydroxide solution(pink)Larutan natrium hidroksida(merah jambu)

Sodium nitrate solution(colourless)Larutan natrium nitrat(tanpa warna)

pH = 13 pH = 7

[3 marks] (ii) What inference can be made based on the answer in (e)(i)?

………………………………………………………………………………………………….[3 marks]

KK0504

(iii) State the operational definition for the end point of titration. Nyatakan definisi secara operasi bagi takat akhir titratan.

…………………………………………………………………………………………………

.………………………………………………………………………………………………...[3 marks]

KK0509

(f) Calculate the average volume and the concentration of nitric acid used in the experiment. Hitung isipadu purata dan kepekatan asid nitrik yang digunakan dalam eksperimen ini.

[3 marks]

(g) (i) If the titrations of sodium hydroxide are repeated using hydrochloric acid and sulphuric acid in the same condition separately to replace nitric acid, predict the volume of hydrochloric acid

and sulphuric acid needed to achieve the end point.Jika titratan natrium hidroksida diulangi, masing-masing menggunakan asid hidroklorik dan

asid sulfurik bagi menggantikan asid nitrik pada keadaan yang sama, ramalkan isipadu asid hidroklorik dan asid sulfurik yang diperlukan bagi mencapai takat akhir.

Volume of hydrochloric acid : ……………… cm3

Isipadu asid hidroklorik:

Volume of sulphuric acid : …………………. cm3

Isipadu asid sulfurik:

[3 marks]

(ii) Give the reasons for the answers in (e)(i) based on acids basicity. Berikan sebab bagi jawapan di (e)(i) berdasarkan kebesan asid.

…………………………………………………………………………………………………..

…………………………………………………………………………………………………..

16 | P a g e A c i d a n d B a s e s

[3 marks]

(h) Table 1.2 shows the pH values of 0.1 mol dm-3 acids solution. Jadual 1.2 menunjukkan nilai pH bagi 0.1 mol dm-3 larutan asid.

Acid pHHydrochloric acidAsid hidroklorik 1.0Sulphuric acid Asid sulfurik 0.7Carbonic acidAsid karbonik 5.5Ethanoic acidAsid etanoik 3.0Nitric acidAsid nitrik 1.0

Table 1.2 Jadual 1.2

Classify these acids into strong acids and weak acids. Kelaskan asid-asid ini kepada asid kuat dan asid lemah.

[3 marks]

17 | P a g e A c i d a n d B a s e s