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Chemistry · 2023 · 2 marks
CBSE 2023 · Region 1 · Set 1 · Q20
(a) On diluting two electrolytes'A'and'B', the Λ_m of'A'increases 25 times while that of'B'increases by 1.5 times. Which of the two electrolytes is…
(a)
On diluting two electrolytes'A'and'B', the $\displaystyle \mathbf{\Lambda}_{\mathrm{m}}$ of'A'increases $\displaystyle 25$ times while that of'B'increases by $\displaystyle 1.5$ times. Which of the two electrolytes is strong? Justify your answer graphically.
OR
(b)
The electrical resistance of a column of $\displaystyle 0.05 \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{NaOH}$ solution of diameter $\displaystyle 1$ cm and length $\displaystyle 50$ cm is $\displaystyle 5.55 \times 10^{3}$ ohm. Calculate the conductivity.
Marking-scheme solution
'B' is a strong electrolyte.
$\displaystyle A = \pi r^2 = 3\cdot14 \times (0\cdot5)^2 = 0\cdot785\ \text{cm}^2$, $\displaystyle \ell = 50\ \text{cm}$
$\displaystyle k = \dfrac{\ell}{R \times A}$
$\displaystyle = \dfrac{50}{0\cdot785 \times (5\cdot55 \times 10^{3})}$
$\displaystyle = 11\cdot47 \times 10^{-3}\ \text{S cm}^{-1}$
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CBSE Class 12 Chemistry past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.