The amount of reactant X remaining in a sealed reaction vessel is recorded over time. A tangent at 80 s passes through the points (40 s,0.072 mol)(40\ \text{s}, 0.072\ \text{mol})(40 s,0.072 mol) and (120 s,0.024 mol)(120\ \text{s}, 0.024\ \text{mol})(120 s,0.024 mol).
What is the rate at which reactant X is used up at 80 s?
6.0×10−4 mol/s6.0 \times 10^{-4}\ \text{mol/s}6.0×10−4 mol/s
4.0×10−4 mol/s4.0 \times 10^{-4}\ \text{mol/s}4.0×10−4 mol/s
9.0×10−4 mol/s9.0 \times 10^{-4}\ \text{mol/s}9.0×10−4 mol/s
1.2×10−3 mol/s1.2 \times 10^{-3}\ \text{mol/s}1.2×10−3 mol/s
127 exam-style questions on AQA GCSE Chemistry 6.1 Rate of reaction, covering 6.1.1a Calculating rates of reactions, 6.1.1b Gradient of a tangent as rate, 6.1.2 Factors which affect the rates of chemical reactions, 6.1.3 Collision theory and activation energy, and 6.1.4 Catalysts. Each one has a worked solution and a mark scheme showing where the marks go.