Monitoring chemical reactions

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Question 1
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A student monitors the rate of the decomposition of hydrogen peroxide:

2H2O2(aq)→2H2O(l)+O2(g) 2\text{H}_2\text{O}_2(\text{aq}) \rightarrow 2\text{H}_2\text{O}(\text{l}) + \text{O}_2(\text{g}) 2H2​O2​(aq)→2H2​O(l)+O2​(g)

by measuring the volume of oxygen gas, VVV (in cm3\text{cm}^3cm3), collected in a gas syringe at regular time intervals.

The reaction is carried out at a constant temperature TTT (in K\text{K}K) and pressure PPP (in kPa\text{kPa}kPa). Let:

  • [H2O2]0[\text{H}_2\text{O}_2]_0[H2​O2​]0​ be the initial concentration of hydrogen peroxide (in mol dm−3\text{mol dm}^{-3}mol dm−3)
  • VsolV_{\text{sol}}Vsol​ be the volume of the reaction mixture (in dm3\text{dm}^3dm3, assumed constant)
  • R R\,R be the gas constant (in J K−1mol−1\text{J K}^{-1} \text{mol}^{-1}J K−1mol−1)

Which of the following expressions correctly gives the concentration of hydrogen peroxide remaining, [H2O2]t[\text{H}_2\text{O}_2]_t[H2​O2​]t​ (in mol dm−3\text{mol dm}^{-3}mol dm−3), at time ttt?

[H2O2]t=[H2O2]0−10−3PVVsolRT[\text{H}_2\text{O}_2]_t = [\text{H}_2\text{O}_2]_0 - \frac{10^{-3} P V}{V_{\text{sol}} R T}[H2​O2​]t​=[H2​O2​]0​−Vsol​RT10−3PV​

[H2O2]t=[H2O2]0−2×10−6PVVsolRT[\text{H}_2\text{O}_2]_t = [\text{H}_2\text{O}_2]_0 - \frac{2 \times 10^{-6} P V}{V_{\text{sol}} R T}[H2​O2​]t​=[H2​O2​]0​−Vsol​RT2×10−6PV​

[H2O2]t=[H2O2]0−2×10−3PVVsolRT[\text{H}_2\text{O}_2]_t = [\text{H}_2\text{O}_2]_0 - \frac{2 \times 10^{-3} P V}{V_{\text{sol}} R T}[H2​O2​]t​=[H2​O2​]0​−Vsol​RT2×10−3PV​

[H2O2]t=[H2O2]0+2×10−3PVVsolRT[\text{H}_2\text{O}_2]_t = [\text{H}_2\text{O}_2]_0 + \frac{2 \times 10^{-3} P V}{V_{\text{sol}} R T}[H2​O2​]t​=[H2​O2​]0​+Vsol​RT2×10−3PV​

Monitoring chemical reactions Questions

  1. GCSE
  2. /Chemistry
  3. /Monitoring chemical reactions