Equal masses of magnesium are reacted separately with excess 1.0 M HCl(aq) at 25 °C
CHEMISTRY · Single correct · A Level · Chemistry · Kinetics · Kinetics
Problem
Equal masses of magnesium are reacted separately with excess 1.0 M HCl(aq) at 25 °C. One trial uses a single magnesium ribbon, and the other uses magnesium powder. The powdered sample produces bubbles of H₂(g) much more rapidly than the ribbon. Which of the following best explains this observation?
(a) Powdering the magnesium lowers the activation energy of the reaction, so collisions are more likely to lead to product.
(b) The powdered magnesium presents a greater total surface area, allowing more frequent effective collisions with H3O+ ions.
(c) The powdered sample contains more magnesium atoms, so the overall reaction order is higher.
(d) The ribbon reacts more slowly because formation of Mg2+ is endothermic for the larger piece.