Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Chemical Formulae, Equations and Calculations Part 1
19 practice questions
Practice questions
1–3 of 3 · Hard
Question 1
2 marks · Hard
Answer and see the solution →The molecular formula of a hydrocarbon is found to be C6H12. State its empirical formula.
Question 2
5 marks · Hard
Answer and see the solution →An experiment is carried out to determine the formula of a hydrated salt, magnesium sulfate crystals, MgSO4·nH2O. The following results are obtained:
Measurement Mass / g Mass of empty crucible 28.60 Mass of crucible + hydrated salt before heating 30.88 Mass of crucible + salt after heating to constant mass (anhydrous MgSO4) 30.00 (Ar: Mg = 24, S = 32, O = 16, H = 1)
(a)[1 mark]Calculate the mass of water lost during heating.
(b)[2 marks]Calculate the number of moles of anhydrous magnesium sulfate (MgSO4) present after heating. (Show your working.)
(c)[2 marks]Determine the value of n in the formula MgSO4·nH2O. (Show your working.)
Question 3
2 marks · Hard
Answer and see the solution →Write the balanced chemical equation, including state symbols, for the reaction of solid sodium with water to form aqueous sodium hydroxide and hydrogen gas.