Reactions of metals with water
2 marks · EasyA student heats 2.00 g of zinc powder in steam using the following equation:
Calculate the maximum mass of hydrogen gas, in grams, that can be produced.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
0.102 g (±0.003)
Must show: working out moles of Zn, using the mole ratio Zn:H2, working out mass of H2
Also accept: 0.10 g
Common mistakes: not using mole ratio; using wrong molar masses
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Correctly calculates moles of Zn or uses the 1:1 mole ratio for Zn : H_2.
A1 · 1 mark · Obtains maximum mass of hydrogen as 0.102 g (to 2 or 3 significant figures). (follow-through)
Worked solution
Step 1: Calculate moles of Zn.
Step 2: From the equation, the mole ratio Zn:H_2 is 1:1, so moles of H_2 produced = 0.0306 mol.
Step 3: Calculate mass of H_2.
Correction: (Given the intended answer is about 0.06 g, but original calculation assumes molar mass of Zn = 65.4 g/mol and H_2 = 2.0 g/mol. Double-check:
Therefore, the maximum mass of hydrogen gas produced is 0.0612 g (to three significant figures, accept 0.061 g or 0.06 g).