Reactions of acids

3 marks · Normal

Magnesium reacts with dilute sulfuric acid to produce magnesium sulfate and hydrogen gas according to the equation:

Calculate the maximum mass of magnesium sulfate (MgSO₄) that can be formed by completely reacting 2.40 g of magnesium with excess dilute sulfuric acid.

Give your answer to 2 decimal places. (Relative atomic masses: Mg = 24.0, S = 32.1, O = 16.0)

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

9.88 g (±0.02)

Also accept: 9.87 g; 9.9 g

Common mistakes: Wrong formula mass for MgSO₄; Incorrect mole ratio; Rounding errors

Show mark scheme and worked solution

Marking points

M1 · 1 mark · Calculates amount (in moles) of magnesium correctly from the given mass.

M2 · 1 mark · Identifies 1:1 mole ratio between Mg and MgSO₄ from the equation, and calculates moles of MgSO₄ formed. (follow-through)

A1 · 1 mark · Calculates correct maximum mass of MgSO₄ to 2 decimal places. (follow-through)

Worked solution

Step 1: Calculate moles of magnesium used.

Step 2: From the equation, 1 mol of Mg produces 1 mol of MgSO₄. So, moles of MgSO₄ formed = 0.100 mol.

Step 3: Calculate formula mass of MgSO₄:

Step 4: Calculate mass of MgSO₄ formed:

Correction: 0.100 mol 120.1 = 12.01 g (this is before checking calculation errors).

Check calculation: 2.40 24.0 = 0.100 mol; 0.100 mol 120.1 = 12.01 g

So the maximum mass of magnesium sulfate formed is 12.01 g (to 2 decimal places: 12.01 g).