A student investigated the rate of reaction between magnesium ribbon and excess hydrochloric acid. The volume of hydrogen gas collected was measured over time.
The results are plotted on the graph below, where a dashed tangent line has been drawn at t=40 st = 40\text{ s}t=40 s.
Which of the following is the rate of reaction at 40 s?
0.50 cm3 s−10.50\text{ cm}^3\text{ s}^{-1}0.50 cm3 s−1
0.60 cm3 s−10.60\text{ cm}^3\text{ s}^{-1}0.60 cm3 s−1
0.85 cm3 s−10.85\text{ cm}^3\text{ s}^{-1}0.85 cm3 s−1
1.18 cm3 s−11.18\text{ cm}^3\text{ s}^{-1}1.18 cm3 s−1
