A 20.0 g impure sample of magnesium carbonate is heated completely and produces 8.0 g of magnesium oxide along with carbon dioxide.
Given: Atomic mass of Mg = 24
What is the percentage purity of MgCO₃ in the sample?

10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. The amount of water produced in this reaction will be:

1. 2 mol

2. 3 mol

3. 4 mol

4. 1 mol

What is the number of moles of PbCl₂ formed when 6.5 g of PbO reacts with 3.2 g of HCl?

1. 0.044
2. 0.333
3. 0.011
4. 0.029