1. Tardigrade
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  4. To 100 mL of 5 M NaOH solution (density 1.2 g/mL) were added 200 mL of another NaOH solution which has a density of 1.5 g/mL and contains 20 mass percent of NaOH. What will be the volume of the gas (at STP) in litres liberated when aluminium reacts with this (final) solution. The reaction is Al + NaOH + H2O → NaAlO2 + 3/2 H2 (At. wt. Na = 23, O = 16, H = 1)

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Q. To 100 mL of 5 M NaOH solution (density 1.2 g/mL) were added 200 mL of another NaOH solution which has a density of 1.5 g/mL and contains 20 mass percent of NaOH. What will be the volume of the gas (at STP) in litres liberated when aluminium reacts with this (final) solution. The reaction is $Al + NaOH + H_2O → NaAlO_2 + 3/2 H_2$
(At. wt. Na $= 23, O = 16, H = 1$)

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Solution:

Moles of $NaOH$ in $1^{st}$ solution $= 0.5\, mol$
Moles of $NaOH$ added $=\frac{200\times1.5\times0.2}{40}=1.5$
Moles of $NaOH$ in the final solution $= 1.5 + 0.5 = 2\, mol$
$Al+NaOH+H_{2}O \rightarrow AaAlO_{2}+\frac{3}{2}H_{2}$
Moles of $H_2$ produced from $2\, mol$ of $NaOH = 3 \,mol$ Volume of $H_2$ produced at $STP = 3 × 22.4 = 67.2\, L$