Q#1. Encircle the Correct answer Which of the following cannot be classified as Arrhenius acid? (a) HNO 3

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Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com)

Chapter # 10 (Acids, Bases and salts) Class 10

th

Q#1. Encircle the Correct answer

(i) Which of the following cannot be classified as Arrhenius acid? (a) HNO3

(b) H2CO3

(c) CO2

(d) H2SO4

(ii) NH3 cannot be classified as a base by

(a) Lewis theory

(b) Bronsted -Lowry theory (c) Arrhenius theory (d) All of these theories

(iii) Which of the following is a Lewis base? (a) BF3

(b) HCl (c) AlCl3

(d) F

-(iv) Choose Lewis acid (a) CN

-(b) NH3

(c) H2O:

(d) H+

(v) A drain cleaner solution contains 1.0x10-8 M, OH- concentration. This Solution is (a) acidic (b) basic (c) neutral (d) cannot be predicted . . . .

(2)

Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com)

(vi) Milk of magnesia contains Mg(OH)2. It is used as antacid. It

neutralizes excess stomach acid. Which salt is formed in this reaction?

(a) MgSO4

(b) MgCO3

(c) MgCl2

(d) MgO

(vii) Ammonia is a base, because it (a) Ionizes in water to give OH- ions

(b) Contains OH group

(c) Can accept an election pair (d) Can accept proton

(viii) Consider the following reaction?

H2O + HCl H3O++ Cl

-Which species is an electron pair acceptor in this reaction? (a) H2O

(b) HCl

(c) H3O+

(d) none

(ix) In the following reaction which species is donating an electron pair? NH3 + BF3 H3N - BF3 (a) H (b) B (c) N (d) BF3

(x) An aqueous solution of NaOH is used as a drain cleaner. If the concentration of OH- ions in this solution is 1.0 x 10-5M, the concentration of H+ ions in it would be?

(a) 1.0 x 10-5M

(3)

Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com) (d) 1.0 x 10-14M

Q#2. Give short answers?

(i) Write the equation for the self-ionization of water.

Ans. Water molecules are highly polar. Occasionally, the collisions between water

molecules are energetic enough to transfer a proton from one water molecule to another.

(ii) Define and give examples of Arrhenius acids.

Ans. According to Arrhenius theory an acid is a substance that ionizes in water to

produce H+. For example,

HCl(g) H+ + Cl-

H2SO4 (l) 2H+(aq) + SO4-2(aq)

(iii) Why H+ ion acts as a Lewis acid?

Ans. According to the Lewis any substance that can accept the pair of electrons is called an acid. H+ acts as a Lewis acid because it accept a pair of electrons in chemical reaction with a Lewis base For example

H+ + :NH3 --- H: NH3 OR [NH4] +

(IV) Why NH3 acts as Bronsted-Lowry base?

Ans. NH3 acts as a Bronsted-Lowry base because it accept a proton when it is reacted with an acid. For example

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(4)

Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com)

(v). Why BF3 acts as Lewis acid?

Ans. BF3 acts as a Lewis acid because it accepts a pair of electrons and all those substances are Lewis acids which accept a pair of electrons. For example

Q#3. Ammonium hydroxide and nitric acid react and produce ammonium nitrate and water. Write balanced chemical equation for this neutralization reaction.

Ans. NH4OH + HNO3 --- NH4NO3 + H2O

Q#4.Write balanced chemical equations for the following neutralization reactions.

(i) Sulphuric acid + Magnesium hydroxide magnesium sulphate + water.

Ans. H2SO4 + Mg (OH) 2 --- MgSO4 + 2H2O

(ii) Sulphuric acid+ Sodium hydroxide Soduimsulphate + water.

Ans. H2SO4 + NaOH --- NaSO4 + H2O

(iii) Hydrochloric acid + calcium hydroxide calcium chloride+ water

Ans. 2HCl + Ca (OH) 2 --- CaCl2 + 2H2O

Q#5. Identify Bronsted –Lowry acids or bases in the following reactions. (i) HNO3 + H2O H3O+ + NO3 + H H N: H F F B _ _ F H H N H F F B _ _ _ F

(5)

Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com)

Ans.In the above reaction HNO3 is a Bronsted-Lowry acid because it donates a proton, while H2O is a Bronsted-Lowry base because it accepts a proton.

(ii) NH3 + HNO3 NH4NO3

Ans. In the above reaction HNO3 is a Bronsted –Lowry acid because it donates a proton, while NH3 is a Bronsted-Lowry base because it accepts a proton.

Q#6. Identify Lewis acid and Lewis base in the following reactions. (i) F- + BF3 [BF4]-

Ans. In the above reaction BF3 is a Lewis acid because it accepts a pair of

electrons while F- is a Lewis base because it donates a pair of electrons.

(ii) H+ +:NH3 [NH4] +

Ans. In the above reaction H+ is a Lewis acid because it accepts a pair of electrons while NH3 is a Lewis base because it donates a pair of electrons.

(iii) :NH3 + AlCl3 [H3N: AlCl3]

Ans. In the above reaction AlCl3 is a Lewis acid because it accepts a pair of electrons while NH3 is a Lewis base because it donates a pair of electrons.

Q#7. Classify the following solutions as acidic, basic or neutral.

(i). A solution that has hydrogen ion concentration 1.0 x10-3 M.

Ans. [H+] = 1x 10 -3 M is greater than 1x 10-7 M so the solution is acidic.

(ii). A solution that has hydrogen ion concentration 1.0 x10-10 M.

Ans. [H+] = 1x10-10 M smaller than 1x10-7 M so the solution is basic.

(iii). A solution that has hydroxyl ion concentration 1.0 x10-3 M.

Ans. If Hydroxide ion concentration is 1 x 10-3 this means that

[H+] = 1x10-11 which is less smaller than 1 x 10-7M so the solution is basic.

(iv). A solution that has hydroxyl ion concentration 1.0 x10-10 M.

Ans. If the Hydroxide ion concentration is 1 x 10-10M then [H+] =1x 10-4 Which is greater than 1 x 10-7M so the solution is acidic?

Q#8. Classify following substance as Lewis acid and bases.

NH3, F-, H2O: , BF3

Ans. Lewis acids: - BF3 is a lewis acid because it has the capability to accept a pair of electrons.

Lewis Base :- NH3 , F- , & H2O are Lewis bases because they have the capability to donate a pair of electrons.

(6)

Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com)

Q#9. Give the Bronsted-Lowry definition of an acid. Write an equation that illustrates the definition.

Ans. According to Bronsted-Lowry theory an acid is specie which donates a proton.

Consider the following example

In the above example H-Cl is Bronsted –Lowry acid because it donate a proton.

Q#10. Identify Bronsted acids and Bronsted bases in the following reactions. (i) CH3COOH (aq) + H2O CH3COO-(aq) + H3O+(aq)

Ans. In the above reaction CH3COOH is a Bronsted-Lowry acid because it donate a proton while H2O is Bronsted-Lowry base because it accept a proton.

(ii) HC (g) + H2O (l)

(aq) + H3O+(aq)

Ans. In the above reaction HCO3- is a Bronsted-Lowry acid because it donate a proton while H2O is a Bronsted-Lowry base because it accept a proton.

(iii) NH3(g) +H2O(l) (aq)+ OH-(aq)

Ans. In the above reaction H2O IS A Bronsted-Lowry acid because it donate a proton while NH3 is Bronsted-Lowry base because it accept a proton.

(iv) HCl(aq) + H (aq) H2CO3(aq) + Cl-(aq)

Ans. HCl is a Bronsted acid because it donate a proton while HCO3- is a Bronsted-Lowry base because it accept a proton in the above reactions.

(v) HS-(aq) + H2O (l) S-2(aq) + H3O+(aq)

Ans. HS- is a Bronsted-Lowry acid because it is proton donor while H2O is a Bronsted-Lowry base because it is proton acceptor .

(7)

Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com)

Ans. H2S is a Brosted-Lowry acid because it is a proton donor while NH3 is a Bronsted-Lowry base because it is proton acceptor.

Q#11. Identify the Lewis acids and the Lewis bases in the following reactions.

(i) Ag+(aq) + 2CN-(aq) Ag (CN2)(aq)

Ans. Ag+ is a Lewis acid because it accepts a pair of electron while CN- is a Lewis base because it donates a pair of electrons.

(ii) B (OH) 3(s) + OH-(aq) B (aq)

Ans. In the above reaction B (OH) 3 is a Lewis acid because it accepts a pair of electrons while OH- is a Lewis base because it is electrons pair donor.

(iii) Cu+2(aq) + 4NH3(aq) [Cu(NH3)4]+2(aq)

Ans. Cu+2 is electrons pair acceptor so it a Lewis acid while NH3 is electrons pair donor so it is a Lewis base.

(iv) OH-(aq) + Al (OH)3(s) Al (aq)

Ans. Lewis acid is Al(OH)3 because it is electrons pair acceptor while OH- is a Lewis base because it is electrons pair donor.

12. Identify Lewis acids and Lewis bases from the following.

Ans. Lewis Acids: - AlCl3, Ag+, FeCl3.

Because all these are electrons pair deficient so they accept a pair of electrons.

Lewis Base:-

All the above are Lewis bases because they all are capable to donate a pair of

electrons.

Q#13. Classify water as proton donor or proton acceptor.

Ans. Water behaves like an acid as well as a base. It is amphoteric in nature.

Substances that react with both acids and bases are called amphoteric substances. Consider the following example in which water is acting as base because it accepts a proton.

. .

AlCl3, Ag+, CH3–. . OH, CH3 – NH2, CN-, OH-, FeCl3

. . . .

(8)

Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com)

While in the following example water donate a proton so it is acting as an acid.

Q#14. Write equations showing the ionization of the following as Arrhenius acids.

(a) HI (aq) (b) HNO2 (aq)

Ans. (a). HI ionizes in water to give Hydrogen ion so it is Arrhenius acid. HI --- H+ + I-

(b). HNO3 ionizes in water to produce Hydrogen ion so t is Arrhenius acid. HNO2 --- H+ + NO2

-Q#15. Write equations showing the ionization of the following as Bronsted-Lowry acids.

(a) HNO2 (aq) (b) HCN (aq)

Ans.

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Sir Amjad Ali (Cell # 55348203, amjad.ali38@yahoo.com) (b) HCN (aq) + H2O ---> H3O+ + CN

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