Electrochemistry Ques 16
16. $4.5 \mathrm{~g}$ of aluminium (at. mass $27 $ $\mathrm{amu}$ ) is deposited at cathode from $\mathrm{Al}^{3+}$ solution by a certain quantity of electric charge. The volume of hydrogen produced at STP from $\mathrm{H}^{+}$ ions in solution by the same quantity of electric charge will be
$[2005]$
(a) $44.8 $ $\mathrm{~L}$
(b) $22.4 $ $\mathrm{~L}$
(c) $11.2 $ $\mathrm{~L}$
(d) $5.6 $ $\mathrm{~L}$
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Answer:
Correct Answer: 16.(d)
Solution: (d) No. of gram equivalent of $\mathrm{H}^{+}=\mathrm{No}$. of eq. of
$ \mathrm{Al}^{3+}=\frac{4.5}{9}=0.5 $
Eq. wt of $\mathrm{Al}^{3+}=\frac{27}{3}=9$
No. of gm eq. of $\mathrm{H}^{+}=$ no. of mole of $\mathrm{H}^{+}$
Hence, Mass of $\mathrm{H}^{+}=0.5 \times 1 \mathrm{~g}=0.5 \mathrm{~g}$
We know that, $2 \mathrm{~g} $ $\mathrm{H}_2$ at $\mathrm{STP}=22.4 \mathrm{~L}$
$ \therefore 0.5 \mathrm{~g} $ $\mathrm{H}_2 \text { at STP }=\frac{22.4}{2}, 0.5=5.6 \mathrm{~L} $
BETA
