Q. No. 10 gram CaCO3 is taken in a one litre container. Active mass of CaCO3 will be (molecular weight of CaCO3 = 100):
1. 0.1
2. 1
3. 0.01
4. 10
The pH of 10-6 M CH3COOH will be:
(ka of CH3COOH = 1.8 \(\times\) 10-5 & log 4.24 =0.63)
1. 5.37
2. 7.0
3. Slightly more than 6
4. 6.95
Case Study:
A buffer solution is defined as a solution whose pH remains practically constant even when small amounts of an acid or a base are added to it.
Types of buffer solutions :
(i) Acidic buffer: It is a solution of a mixture of a weak acid and a salt of this weak acid with a strong base (e.g. CH3COOH + CH3COONa)
(ii) Basic buffer: It is the solution of a mixture of a weak base and a salt of this weak base with a strong acid (e.g. NH4OH + NH4Cl)
Henderson's equation is used to determine pH of buffer mixtures of differ types:
for acidic buffer Henderson's equation is
pH= pKa + log \([Salt] \over [Acid]\) (ka = ionisation constant of weak acid )
for basic buffer Henderson's equation is :
POH = Pkb + log \([Salt] \over [Base]\) (kb = ionisation constant of weak base )
How many moles of HCl are required with 0.01 mole NaCN to prepare a buffer solution of pH =9?
(ka of HCN = \(1 \times 10^{-10}\))
1. 0.009
2. 0.09
3. 0.9
4. Buffer solution cannot formed
1. 0.25 Mol/L
2. \({1 \over 22.4 } Mol /L\)
3. 0.175 Mol/L
4. \({ 1 \over 5.6}~ Mol / L\)
1. \(NaCl\)
2. \(CH_3COONH_4\)
3. \(Na_2SO_4 \)
4. None of these
| Assertion (A): | For the reaction: H2(g) + I2(g) \(\rightleftharpoons\) 2HI(g), if the volume of the vessel is reduced to half of its original volume, the equilibrium concentration of all gases will be doubled. |
| Reason (R): | According to Le-Chatelier's principle, reaction shifts in a direction that tends to minimize the effect of stress. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | (A) is False but (R) is True. |
| Assertion (A): | Salts of strong acid and strong base do not undergo hydrolysis. |
| Reason (R): | These salts undergo hydration. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | Both (A) and (R) are False. |
(pKa = 4.75)
1. 5.05
2. 4.15
3. 5.35
4. 4.75
| Assertion (A): | The solubilities of two sparingly soluble salts, Ni(OH)2 and AgCN with Ksp of \(4 \times 10^{-8} ~and~1 \times 10^{-10}~mol/L\) respectively. |
| Reason (R): | AgCN is less soluble than Ni(OH)2 |
| 1. | Both (A) and (R) are correct and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are correct but (R) is not the correct explanation of (A). |
| 3. | (A) is correct but (R) is not correct. |
| 4. | (A) is not correct but (R) is correct. |
The rapid change of pH near the stoichiometric point of an acid-base titration is the basis of indicator detection. pH of the solution is related to the ratio of the concentrations of the conjugate acid (HIn) and base (In–) forms of the indicator by the expression:
1.
2.
3.
4. All of the above.
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