Question 1: What is ionic products of water?
Answer 1: Kw = [H+] [OH–]
Question 2: Write conjugates acids of H2O & NH3.
Answer 2: H3O+ & NH4+.
Question 3: Define Arrhenius acids.
Answer 3: Arrhenius acids are the substances that ionize in water to form H+.
Question 4: Define the term degree of ionization.
Answer 4: Extent up to which an acid/base/salt ionize to form ions.
Question 5: What are Buffer solutions?
Answer 5: The solutions which resist change in pH on dilution or with the addition of small amounts of acid or alkali are called Buffer Solutions.
Question 6: Out of H2O & H3O+ which is stronger acid?
Answer 6: H3O+.
Question 7: What is common ion effect?
Answer 7: Shift in equilibrium on adding a substance that provides more of an ionic species already present in the dissociation equilibrium.
Question 8: Classify the following bases as strong and weak bases:
NaHCO3, NaOH, KOH, Ca(OH) 2, Mg(OH) 2.
Answer 8: Strong bases : NaOH, KOH
Weak bases : NaHCO3, Ca(OH)2, Mg(OH)2.
Question 9: The concentration of hydrogen ion in a sample of soft drink is 3.8 × 10–3 M. What is its pH?
Answer 9:
pH = – log [3.8 × 10–3 ]
= – {log[3.8] + log[10–3] }
= – {(0.58) + (– 3.0)}
= – {– 2.42}
= 2.42
Therefore, the pH of the soft drink is 2.42 and it is acidic.
Question 10: Explain Lewis acids and bases with suitable examples.
Answer 10: Lewis acids are lone pair (of e-) accepters while Lewis bases are lone pair donators. AlCl3 is a Lewis acid while NH3 is a Lewis base.
Question 11: What is difference between alkali and bases? Give examples.
Answer 11: An alkali is a water soluble base. All the alkalis are bases but all the bases are not alkali. For example NaOH is an alkali/base. Ca(OH)2 is a base but not an alkali.
Question 12: The pH of some common substances is given bellow. Classify the substances as acidic/basic.
Name of fluid pH
Lime water 10
Milk of magnesia 10
Human saliva 6.4
Vinegar 3
Lemon juice 2.2
Sea water 7.8
Answer 12: Acidic : Human saliva, Lemon juice, vinegar
Basic : Lime water, sea water, milk of magnesia.
Question 13: Explain general characteristics of acids and bases.
Answer 13: Most of the acids taste sour. Acids are known to turn blue litmus paper into red and liberate dihydrogen on reacting with some metals. Bases are known to turn red litmus paper blue, taste bitter and feel soapy.
Question 14: Water is amphoteric in nature. Explain.
Answer 14: Water can react with acid as well as base.
Water is basic as H2O + HCl → H3O+ + Cl– .
Water is acidic as H2O + NH3 → OH– + NH4+.
Question 15: Classify the following species into Lewis acids and Lewis bases and show how these act as such: a) HO– b) F– c) H+ d) BCl3
Answer 15:
a) Hydroxyl ion is a Lewis base as it can donate an electron lone pair (OH–).
b) Fluoride ion acts as a Lewis base as it can donate any one of its four electron lone pairs.
c) A proton is a Lewis acid as it can accept a lone pair of electrons from bases like hydroxyl ion and fluoride ion.
d) BCl3 acts as a Lewis acid as it can accept a lone pair of electrons from species like ammonia or amine molecules.
Question 16: Explain the following:
(i) Common ion effect (ii) Solubility products (iii) pH
Answer 16:(i) Suppression of ionization of weak electrolyte by adding a strong electrolyte having an ion common.
(ii) Product of the molar concentrations of the ions in a saturated solution, each concentration term raised to the power equal to the no. of ions produced.
(iii) Negative logarithm of hydrogen ion concentration.
Answer 1: Kw = [H+] [OH–]
Question 2: Write conjugates acids of H2O & NH3.
Answer 2: H3O+ & NH4+.
Question 3: Define Arrhenius acids.
Answer 3: Arrhenius acids are the substances that ionize in water to form H+.
Question 4: Define the term degree of ionization.
Answer 4: Extent up to which an acid/base/salt ionize to form ions.
Question 5: What are Buffer solutions?
Answer 5: The solutions which resist change in pH on dilution or with the addition of small amounts of acid or alkali are called Buffer Solutions.
Question 6: Out of H2O & H3O+ which is stronger acid?
Answer 6: H3O+.
Question 7: What is common ion effect?
Answer 7: Shift in equilibrium on adding a substance that provides more of an ionic species already present in the dissociation equilibrium.
Question 8: Classify the following bases as strong and weak bases:
NaHCO3, NaOH, KOH, Ca(OH) 2, Mg(OH) 2.
Answer 8: Strong bases : NaOH, KOH
Weak bases : NaHCO3, Ca(OH)2, Mg(OH)2.
Question 9: The concentration of hydrogen ion in a sample of soft drink is 3.8 × 10–3 M. What is its pH?
Answer 9:
pH = – log [3.8 × 10–3 ]
= – {log[3.8] + log[10–3] }
= – {(0.58) + (– 3.0)}
= – {– 2.42}
= 2.42
Therefore, the pH of the soft drink is 2.42 and it is acidic.
Question 10: Explain Lewis acids and bases with suitable examples.
Answer 10: Lewis acids are lone pair (of e-) accepters while Lewis bases are lone pair donators. AlCl3 is a Lewis acid while NH3 is a Lewis base.
Question 11: What is difference between alkali and bases? Give examples.
Answer 11: An alkali is a water soluble base. All the alkalis are bases but all the bases are not alkali. For example NaOH is an alkali/base. Ca(OH)2 is a base but not an alkali.
Question 12: The pH of some common substances is given bellow. Classify the substances as acidic/basic.
Name of fluid pH
Lime water 10
Milk of magnesia 10
Human saliva 6.4
Vinegar 3
Lemon juice 2.2
Sea water 7.8
Answer 12: Acidic : Human saliva, Lemon juice, vinegar
Basic : Lime water, sea water, milk of magnesia.
Question 13: Explain general characteristics of acids and bases.
Answer 13: Most of the acids taste sour. Acids are known to turn blue litmus paper into red and liberate dihydrogen on reacting with some metals. Bases are known to turn red litmus paper blue, taste bitter and feel soapy.
Question 14: Water is amphoteric in nature. Explain.
Answer 14: Water can react with acid as well as base.
Water is basic as H2O + HCl → H3O+ + Cl– .
Water is acidic as H2O + NH3 → OH– + NH4+.
Question 15: Classify the following species into Lewis acids and Lewis bases and show how these act as such: a) HO– b) F– c) H+ d) BCl3
Answer 15:
a) Hydroxyl ion is a Lewis base as it can donate an electron lone pair (OH–).
b) Fluoride ion acts as a Lewis base as it can donate any one of its four electron lone pairs.
c) A proton is a Lewis acid as it can accept a lone pair of electrons from bases like hydroxyl ion and fluoride ion.
d) BCl3 acts as a Lewis acid as it can accept a lone pair of electrons from species like ammonia or amine molecules.
Question 16: Explain the following:
(i) Common ion effect (ii) Solubility products (iii) pH
Answer 16:(i) Suppression of ionization of weak electrolyte by adding a strong electrolyte having an ion common.
(ii) Product of the molar concentrations of the ions in a saturated solution, each concentration term raised to the power equal to the no. of ions produced.
(iii) Negative logarithm of hydrogen ion concentration.
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