Question

Consider the following statements
a) The pH of a mixture containing 400 ml of 0.1M ${{H}_{2}}S{{O}_{4}}$ and 400 ml of 0.1 NaOH will be approximately 1.3
b) Ionic products of water are temperature dependent.
c) A monobasic acid with ${{K}_{a}}={{10}^{-5}}$ has a pH = 5. The degree of dissociation of this acid is 50%.
d) The Le Chatelier’s principle is not applicable to common-ion effect.
The correct statements are:
A. a, b and d
B. a and b
C. a, b and c
D. b and c

Answer 1

Hint:. When a force is applied to a chemical system at equilibrium, the equilibrium will shift to relieve the force applied; this principle is known as Le Chatelier′s Principle. In simple terms we can say that it can be used to predict the direction of a chemical reaction in response to a change in conditions.

Complete step by step answer:
To identify the correct statements we have to discuss all the statements one by one:
a. The pH of a mixture containing 400 ml of 0.1M ${{H}_{2}}S{{O}_{4}}$ and 400 ml of 0.1 NaOH will be approximately 1.3
The reaction of this equation can be shown as:
$2NaOH+{{H}_{2}}S{{O}_{4}}\to N{{a}_{2}}S{{O}_{4}}+2{{H}_{2}}O$

$[{{H}^{+}}]=\dfrac{20\times {{10}^{-3}}\times {{10}^{3}}\times 2}{800}$
$[{{H}^{+}}]=\dfrac{1}{20}$
$-\log [{{H}^{+}}]=-\log \dfrac{1}{20}$
pH = log 20
pH = 1.3
Hence this statement is correct.

b. Ionic product of water is temperature dependent
As we know that ionic products increase with increase in temperature, so we can say that it is temperature dependent.
Statement B is also correct

c. A monobasic acid with ${{K}_{a}}={{10}^{-5}}$has a pH = 5. The degree of dissociation of this acid is 50%
pH = 5
$[{{H}^{+}}]=c\alpha ={{10}^{-5}}$
${{K}_{\alpha }}=\dfrac{c{{\alpha }^{2}}}{(1-\alpha )}$
\[K=\dfrac{[{{H}^{+}}]\alpha }{(1-\alpha )}\]
\[{{10}^{-5}}=\dfrac{{{10}^{-5}}\times \alpha }{(1-\alpha )}\]
\[1=2\alpha ;\alpha =0.5\]
Hence statement C is also correct.

d. Le Chatelier’s principle is not applicable to common-ion effect: This statement is not correct because Le Chatelier’s principle is applicable to common-ion effect.
So, the correct answer is “Option C”.

Note: The ionic product is the product of concentrations of ionic species in either a saturated or an unsaturated solution. When only the saturated solutions are considered, the ionic product is known as the solubility product.