Assertion And Reason. - Chemistry STD 12 Questions - Vidyadip

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Assertion And Reason.

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15 questions · timed · auto-graded

Question 11 Mark

Assertion(A): Buffer mixture is the one whose pH remains constant even by addition of strong acid or strong base.
Reason (R): To resist changes in its pH on the addition of an acid or base, the buffer solution should contain both acidic as well as basic components so as to neutralise the effect of added acid or base.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 21 Mark

Assertion(A): A mixture of $CH _3 COOH$ and $CH _3 COONH _4$ is an acidic buffer.
Reason (R): An acidic buffer contains a weak acid and the salt of weak acid with strong base.
(a) A is correct but R is wrong.
(b) A is wrong but R is correct.
(c) Both A and R are correct and R is the correct explanation of A
(d) Both A and R are wrong

Answer

(b) A is wrong but R is correct.

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Question 31 Mark

Assertion(A): pH = 7 signifies pure water.
Reason (R): pH = 7 means it is a neutral solution where$\left[ H _3 O ^{+}\right]\left[ OH ^{-}\right]$
(a) A is correct but R is wrong
(b) A is wrong but R is correct
(c) Both A and R are wrong
(d) A is correct and R does not explain A

Answer

(b) A is wrong but R is correct

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Question 41 Mark

Assertion(A): The solution of $NH _4 Cl$ has pH value less than 7 .
Reason (R): The salt of weak base $\left( NH _4 OH \right)$ and strong acid $( HCl )$ is acidic in nature, when dissolved in water. So pH value is less than 7 .
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 51 Mark

Assertion(A): The addition of sodium acetate to acetic acid solution leads to the suppression in the dissociation of acetic acid.
Reason (R): This is due to common ion effect. i.e., $CH _3 COOH$ and $CH _3 COONa ^{-}$both contains $CH _3 COO ^{-}$ion as common.
(a) Both A and R are correct and R is the correct explanation of A
(b) BothA and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 61 Mark

Assertion(A): When dilution increases, the degree of dissociation of weak electrolyte also increases.
Reason (R): The degree of dissociation a is inversely proportional to concentration c. When the dilution increases by 100 times, the dissociation increases by 10 times.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 71 Mark

Assertion(A): With the increase in temperature, the ionic product of water also increases.
Reason (R): The dissociation of water is an endothermic reaction.
(a) Both A and R are correct and R is the correct explanation of A
(b) A is correct but R is wrong
(c) A is wrong but R is correct
(d) Both A and R are wrong

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 81 Mark

Assertlon(A): HCl is an strong acid while HCOOH is a weak acid.
Reason (R): HCI is completely ionised in water whereas HCOOH is paritally ionised in water.
(a) Both A and R are wrong
(b) A is wrong but R is correct
(c) A is correct but R is wrong
(d) Both A and R are correct and R is the correct explanation of A

Answer

(d) Both A and R are correct and R is the correct explanation of A

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Question 91 Mark

Assertion(A): $NH _3, H _2 O , ROH$ all are examples of Lewis bases.
Reason (R): Molecules with one or more lone pairs of electrons act as Lewis bases.
(a) Both A and R are wrong
(b) A is correct and R is the correct explanation of A.
(c) A is wrong but R is correct.
(d) A is correct but R is wrong

Answer

(b) A is correct and R is the correct explanation of A.

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Question 101 Mark

Assertion(A): $SiF _4$ can act as Lewis acid.
Reason (R): In $SiF _4$ the central atom can expand its octet due to the availability of empty d – orbitais and can accept a pair of electrons.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 111 Mark

Assertion(A): in coordination compounds, the ligands acts as Lewis acid aid the central metal atom or ion act as Lewis base.
Reason (R): Ligands are capable of accepting of a pair of electrons donated by the central metal atom or ion.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is not the correct explanation of A.
(d) A is wrong but R is correct.

Answer

(b) Both A and R are wrong

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Question 121 Mark

Assertion $( A ): BF _3$ is a Lewis acid.
Reason (R): Boron has a vacant 2p orbital to accept the lone pair of electrons donated by any substance to form a new coordinate covalent bond.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong .
(c) A is correct but R is not the correct explanation of A.
(d) A is wrong but R is correct.

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 131 Mark

Assertion (A): In the reaction $HCl + H _2 O \rightleftharpoons H _3 O ^{+}+ Cl ^{-}, HCl ^{-}$and $Cl ^{-}$are conjugate acid - base pair.
Reason (R): By Lowry – Bronsted theory, chemical species that differ only by a proton are called conjugate acid – base pair.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is not the correct explanation of A
(d) A is wrong but R is correct.

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 141 Mark

Assertion(A): When ammonia dissolved in water, H20 acts as an acid.
Reason (R): When ammonia is dissolved in water, it accepts a proton from water. According to Lowry – Bronsted theory, proton donor is acid and so water act as an acid.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is not the correct explanation of A.
(d) A is wrong but R is correct. .

Answer

(a) Both A and R are correct and R is the correct explanation of A

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Question 151 Mark

Assertion(A): In the process of dissolution of HCl in water, HCl act as acid and $H_2O$ act as base.
Reason (R): When HCl is dissolved in water, it donates a proton to water.
(a) Both A and R are correct and R explains A
(b) Both A and R are wrong
(c) A is correct but R is not the correct explanation of A.
(d) A is wrong but R is correct.

Answer

(a) Both A and R are correct and R explains A

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Assertion And Reason. - Chemistry STD 12 Questions - Vidyadip