IB Chemistry HL 1.5.4 Ideal Gas Equation 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.

Syllabus
First assessment 2025
Course
Chemistry HL
Level
HL

Exam points

  • Rearrange PV=nRT to calculate pressure, volume, amount or molar mass using kelvin temperature and consistent pressure and volume units.
  • Use fixed-mass gas relationships and ideal-gas graphs at constant pressure or temperature, converting Celsius to kelvin.
  • Apply PV=nRT or a combined-gas-law ratio when gas amount or conditions change, checking units and significant figures.

IB Chemistry HL 1.5.4 Ideal Gas Equation Questions question 1

[Maximum number: 3]

A group of students investigated the rate of the reaction between aqueous sodium thiosulfate and hydrochloric acid according to the equation below.

Na2 S2O3(aq)+2HCl(aq)2NaCl(aq)+SO2( g)+S( s)+H2O(1)\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}(\mathrm{aq})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{SO}_{2}(\mathrm{~g})+\mathrm{S}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(1)

The two reagents were rapidly mixed together in a beaker and placed over a mark on a piece of paper. The time taken for the precipitate of sulfur to obscure the mark when viewed through the reaction mixture was recorded.

Figure for Question IB Chemistry HL 1.5.4 Ideal Gas Equation Questions question 1 — IB Chemistry HL
Figure for Question IB Chemistry HL 1.5.4 Ideal Gas Equation Questions question 1 — IB Chemistry HL

Initially they measured out 10.0 cm310.0 \mathrm{~cm}^{3} of 0.500moldm30.500 \mathrm{moldm}^{-3} hydrochloric acid and then added 40.0 cm340.0 \mathrm{~cm}^{3} of 0.0200 moldmm30.0200 \mathrm{~mol} \mathrm{dm} \mathrm{m}^{-3} aqueous sodium thiosulfate. The mark on the paper was obscured 47 seconds after the solutions were mixed.

Another group suggested collecting the sulfur dioxide and drawing a graph of the volume of gas against time.

Calculate the volume of sulfur dioxide, in cm3\mathrm{cm}^{3}, that the original reaction mixture would produce if it were collected at 1.00×105 Pa1.00 \times 10^{5} \mathrm{~Pa} and 300 K .

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