10th. Chemistry. Ch.10. Exercise Solved (Malik Xufyan) Cell # 03137355727

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Chapter # 10
Acid, Bases and Salts
Q.1. Name three common household substances having
a) pH value greater than 7
b) pH value less than 7
c) pH value equal to 7
Ans.
a) pH value greater than 7
i. eggs, baking soda, bleach , soapy water etc
b) pH value less than 7
black coffee, bananas, orange juice, soda, lemon juice, vinegar, milk
c) pH value equal to 7
Pure water,
Q.2. Define a base and explain all alkalies are bases but all bases are not alkalies.
Ans.
Base: A substance which have ability to gain electron pair or give hydroxyl ion, or accept
proton.
All alkalies are bases but all bases are not alkalies. Because water soluble base is called alkali.
All bases are not soluble in water that’s why Alkali metals are bases and all bases are not
alkalies.
Q.3. Define Bronsted-lowry base and explain with an example that water is Bronsted-
Lowry base.
Ans.
Bronsted Base: a base is substance that an accept a proton (H+
) from another substance.
Example: when HCl dissolve in water ; HCl acts as an acid and H20 as a base.
HCl + H2O H3O+
+ Cl-
Acid base conjugate acid conjugate base

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It is reversible reaction. In the forward reaction HCl is an acid as it donates a proton, whereas
H2O is an base as it accept a proton.
Q.4. How can you justify that Bronsted Lowry concept of acid and base is applicable to non
aquous solution
Ans
when HCl dissolve in NH3 to form NH4Cl
HCl + NH3 NH4Cl
In this example, HCl acts as an acid and NH3 as a base. This theory works for all protic solvents
(acetic acid, water, liquid ammonia, etc,) not only for water as Arrhenius theory. But it does not
explain the acid base behavior in aprotic solvents such as benzene and dioxane.
Q.5. Which kind of bond forms between Lewis acid and a base?
Ans.
According to Lewis concept:
In these reaction, it is donation and acceptance of an electron pair to form a coordinate covalent
bond in an adduct. Acid are electron pair acceptor while bases are electron pair donor.
Q.6. why H+
ion acts as a Lewis acid?
Ans. Because H+
ion has no electron in there shell. It has ability to gain or accept pair of
electron. That’s why H+
ion acts as a Lewis acid.
Q.7. Name two acids used in the manufacturing of fertilizers.
Ans. Nitric acid and sulphuric acid are used for the manufacturing of fertilizers.
Q.8. Define pH. What is pH of pure of water?
Ans.
pH: pH is negative logarithm of molar concentration of the Hydrogen ions. That is
pH = - log [H+
]
Q.9. How many times a solution of pH 1 will be stronger than that of solution having pH 2?
Ans. A solution of pH 1 has 10 times higher concentration of [H+
] than that of a solution of pH
2. Hence low pH value means strong acid while high pH value means a strong base and vice
versa.
Q.10. Define Following

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i. Normal salts
ii. Basic salts
Normal salts: A salt formed by the total replacement of ionizable H+
ions of an acid by positive
metal ion or NH+
ions is called normal or neutral salts. These salts are neutral to litmus.
Example:
HCl(aq) + KOH(aq) KCl(aq) + H2O(l)
Basic Salts: Basic salts are formed by the incomplete neutralization of polyhydroxy base by an
acid.
Example:
Al(OH)3(aq) + HCl(aq) Al(OH)2Cl(aq) + H2O(l)
Q.11. Na2SO4 is neutral salt while NaHSO4 an acidic salt. Justify
Ans. According to neutral or normal salts: Na2SO4 is formed by the total replacement of
ionizable H+
ions of an acid by positive metal ion.
H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l)
According to acidic salt:
NaHSO4 is formed by the partial replacement of a replaceable H+
ions of an acid by a positive
metal ion.
H2SO4(aq) + KOH(aq) NaHSO4(aq) + H2O(l)
Q.12. Give few characteristic properties of salts.
Ans. There are few characteristic properties:
1. Salts are ionic compound found in crystalline form.
2. They have high melting and boiling points.
3. Salts are neutral compounds. Although, they do not compose of equal number of positive
and negative ions, but have equal number of positive and negative charges.

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4. Most of salts contain water of crystallization which is responsible for the shape of the
crystals. Number of molecules of water are specific for each salt and they are written with
the chemical formula of a salt .
Q.13. How are soluble salts are recovered from water?
Ans. Soluble salts are often prepared in water. Therefore, they are recovered by evaporation or
crystallization.
There are three methods for this:
a. By the reaction of an acid and a metal ( Direct displacement method)
b. By the reaction of an acid and a base (Neutralization method)
c. By the reaction of an acid and metallic oxide
Q.14. How insoluble salts are prepared?
Ans. In this method, usually solutions of soluble salts are mixed. During the reaction exchange of
ionic radicals (i.e., metallic radicals exchange with acid radicals) takes place to produce two new
salts. One of the salt is insoluble and the other is soluble. The insoluble salt precipitates (solidify
in solution).
AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
Q.15. Why salt is neutral? Explain with an example.
Ans.
According to neutral salt:
A salt formed by the total replacement of ionizable H+
ions of an acid by positive metal ion or
NH+
ions is called normal or neutral salts. These salts are neutral to litmus.
Example:
HCl(aq) + KOH(aq) KCl(aq) + H2O(l)
Q.16. Name an acid used in the preservation of food.
Ans. Benzoic acid and acetic acid is used for food preservation.
Q.17. Name the acid present in
i. vinegar ii. Ant sting iii. Citrus fruits iv. Sour milk

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Ans.
Acetic acid in vinegar,formic acid in ant sting, citric acid in citrus fruits and lactic acid in sour
milk.
Q.18. How can you justify that Pb(OH)NO3 is a basic salt?
According to basic salt : Pb(OH)NO3 is formed by the incomplete neutralization of polyhydroxy
base by nitric acid.
Pb(OH)2(aq) + HNO3(aq) Pb(OH)NO3(aq) + H2O(l)
Q.19. You are in a need of an acidic salt. How can you prepare it?
Ans. According to acidic salt:
NaHSO4 is formed by the partial replacement of a replaceable H+
ions of an acid by a positive
metal ion.
H2SO4(aq) + KOH(aq) NaHSO4(aq) + H2O(l)
Q.20. Which salt is used to prepare plaster of Paris?
Ans. Gypsum is used to prepare plaster of Paris which is used for making statues, casts, etc.