IB Chemistry SL 1.4.6 Avogadros Law Questions

Relate equal gas volumes at the same temperature and pressure to equal amounts, then use balanced-equation volume ratios and molar volume at STP/SATP.

Exam points

Relate equal volumes of gases at the same temperature and pressure to equal amounts and numbers of molecules.
Use balanced-equation gas-volume ratios to calculate reactant or product gas volumes and identify limiting gas quantities.
Convert between gas amount and volume using molar volume at STP or SATP, with consistent units and significant figures.

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Two hydrides of nitrogen are ammonia and hydrazine, $\mathrm{N}_{2} \mathrm{H}_{4}$ . One derivative of ammonia is methanamine whose molecular structure is shown below.

Figure for Question IB Chemistry SL 1.4.6 Avogadros Law Questions question 1 — IB Chemistry SL

Calculate, showing your working, the mass of hydrazine needed to remove all the dissolved oxygen from $1000 \mathrm{dm}^{3}$ of the sample.

Calculate the volume, in $\mathrm{dm}^{3}$ , of nitrogen formed under SATP conditions.
(The volume of 1 mol of gas $=24.8 \mathrm{dm}^{3}$ at SATP.)

\mathrm{n}(\mathrm{N_2H_4})=\mathrm{n}(\mathrm{O_2})=\frac{8.0\,\mathrm{g}}{32.00\,\mathrm{g\,mol^{-1}}}=0.25\,\mathrm{mol}

V(\mathrm{N_2})=0.25\,\mathrm{mol}\times24.8\,\mathrm{dm^3\,mol^{-1}}=6.2\,\mathrm{dm^3}

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IB Chemistry SL 1.4.6 Avogadros Law Questions question 1