Paper 2 · Stoichiometry and Mole Calculations
In an experiment, 2.4 g of magnesium (Mr = 24) reacts completely with a sample of black solid copper(II) oxide (Mr = 80), according to Mg + CuO -> MgO + Cu. What mass of copper(II) oxide reacted?
A8 g
B6.4 g
C16 g
D4.0 g
Explanation: Moles Mg = 2.4/24 = 0.1; the 1:1 ratio in Mg + CuO -> MgO + Cu gives 0.1 mol CuO; mass = 0.1 x 80 = 8 g.
Derived from ZIMSEC Chemistry 5071/2 Paper 2 Theory, November 2013, Q3
