O-LevelChemistryRates of Reaction5070/22 · Oct/Nov 2022 · Q610 Marks

This question is about nitrogen and oxides of nitrogen.

(a)State the percentage of nitrogen by volume in dry air.[1]
(b)The equation represents the equilibrium between nitrogen and oxygen at a high temperature in a closed container. N2(g) + O2(g) ⇌ 2NO(g)
(b)(i)Predict what happens to the position of equilibrium when the pressure is increased. Explain your answer. prediction explanation[2]
(b)(ii)The table shows the concentration of nitrogen(II) oxide, NO, in the closed container at three different temperatures. [Table of temperature vs concentration of NO] State what this information shows about the enthalpy change of the forward reaction. Explain your answer. enthalpy change explanation[2]
(c)Nitrogen(II) oxide, NO, reacts with hydrogen to produce ammonia and water. Construct the equation for this reaction.[2]
(d)Nitrogen oxides are pollutants in the atmosphere.
(d)(i)State one source of nitrogen oxides in the atmosphere.[1]
(d)(ii)Nitrogen oxides contribute to acid rain. State one effect of acid rain on buildings.[1]
(d)(iii)State the formula of the ion that is present in all acids.[1]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2022). The mark or mark type is shown in brackets.

[1] 6(a) 78(%)
[2] 6(b)(i) no effect (on position of equilibrium) (1); equal number of moles of gas on each side of the equation / equal volumes of gas on each side of the equation (1)
[2] 6(b)(ii) the reaction is endothermic (1); because there is a higher concentration of (NO) at higher temperatures / there is a lower concentration of N2 and O2 at lower temperatures (1)
[2] 6(c) 2NO + 5H2 → 2NH3 + 2H2O; correct formulae (1); correctly balanced (1)
[1] 6(d)(i) car exhaust fumes / vehicle engines / fossil fuel powered power stations
[1] 6(d)(ii) (chemical) erosion / corrosion
[1] 6(d)(iii) H+

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