M.C.Q (1 Marks)

MCQ 1511 Mark

Fear or excitement generally causes one to breathe rapidly and it results in the decrease of concentration of $\ce{CO_2}$ in blood. In what way, it will change the $\ce{pH}$ of blood?

A
$\ce{pH}$ will increase
B
$\ce{pH}$ will decrease
✓
No change
D
$\ce{pH}$ will be $7$

Answer

Correct option: C.

No change

As we know, $\ce{CO_2}$ is acidic in nature. So, a decrease in its concentration should increase the $\ce{pH}.$ But, blood contains serum which has proteins in it. This acts as a buffer solution. We already know that buffer solutions resist a change in the $\ce{pH}$ even on addition of a small amount of acid or small amount of base or dilution, etc.

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MCQ 1521 Mark

$0.10M \ \ce{CH_3COOH}$ is $1.34\%$ ionised, calculate its $\ce{K_a}$ :

✓
$ 1.8 \times 10^{-5} $
B
$ 1.8 \times 10^{-4} $
C
$ 5 \times 10^{-4} $
D
$ 4 \times 10^{-5} $

Answer

Correct option: A.

$ 1.8 \times 10^{-5} $

$\text{K}_{\text{a}}=\text{C}\alpha^2=0.1\times\frac{1.34}{100}\times\frac{1.34}{100}=1.795\times10^{-5}$

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MCQ 1531 Mark

Which of the following is not a buffer solution?

A
$ \mathrm{CH}_3 \mathrm{COOH}+\mathrm{CH}_3 \mathrm{COONa} $
B
$ \mathrm{H}_3 \mathrm{BO}_3+\mathrm{Na}_3 \mathrm{BO}_3 $
✓
$\mathrm{HClO}_4+\mathrm{NaClO}_4 $
D
$ \mathrm{NH}_4 \mathrm{OH}+\left(\mathrm{NH}_4\right)_2 \mathrm{SO}_4 $

Answer

Correct option: C.

$\mathrm{HClO}_4+\mathrm{NaClO}_4 $

A buffer solution is a mixture of a weak acid or a weak base and its salt.
In the given question, $\mathrm{CH}_3 \mathrm{COOH}$ and $\mathrm{H}_3 \mathrm{BO}_3$ are weak acids whereas $\mathrm{NH}_4 \mathrm{OH}$ is a weak base. $\mathrm{HClO}_4$ is a strong acid, its mixture with its salt cannot be a buffer solution according to the definition of buffer solution.

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Chemistry M.C.Q (1 Marks)