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CBSE 12th Chemistry Delhi Set 1 - 2023
Subjective
+4
-0

Rahul set-up an experiment to find resistance of aqueous $$\mathrm{KCl}$$ solution for different concentrations at $$298 \mathrm{~K}$$ using a conductivity cell connected to a Wheatstone bridge. He fed the Wheatstone bridge with a.c. power in the audio frequency range 550 to 5000 cycles per second. Once the resistance was calculated from null point he also calculated the conductivity $$K$$ and molar conductivity $$\wedge_m$$ and recorded his readings in tabular form.

S.No. Conc. (M) $$\mathrm{k~S~cm^{-1}}$$ $$\mathrm{\wedge_m~S~cm^2~mol^{-1}}$$
1. $$1.00$$ $$111.3\times10^{-3}$$ $$111.3$$
2. $$0.10$$ $$12.9\times10^{-3}$$ $$129.0$$
3. $$0.01$$ $$1.41\times10^{-3}$$ $$141.0$$

(a) Why does conductivity decrease with dilution?

(b) If $$\wedge_{\mathrm{m}}{ }^0$$ of $$\mathrm{KCl}$$ is $$150.0 \mathrm{~S} \mathrm{~cm} \mathrm{~mol}^{-1}$$, calculate the degree of dissociation of $$0.01 \mathrm{M} \mathrm{KCl}$$.

(c) If Rahul had used $$\mathrm{HCl}$$ instead to $$\mathrm{KCl}$$ then would you except the $$\wedge_{\mathrm{m}}$$ values to be more or less than those per $$\mathrm{KCl}$$ for a given concentration. Justify.

OR

(c) Amit, a classmate of Rahul repeated the same experiment with $$\mathrm{CH}_3 \mathrm{COOH}$$ solution instead of $$\mathrm{KCl}$$ solution. Give one point that would be similar and one that would be different in his observations as compared to Rahul.

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Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
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