IGCSE - Chemical calculations

True or False? "One mole of oxygen contains more molecules than one mole of hydrogen"

• True

• False

The molecular formula of butanoic acid is C₄H₈O_2. What is its empirical formula?

• C₂H₄O

• CH₂O

• CHO

What is the relative formula mass (Mr) of KOH? Relative atomic masses (Ar): H=1, O=16, K=39

• 39

• 28

• 56

In the following example, what physical state is the hydrochloric acid in?

Mg_(s) + 2HCl_(aq) --> MgCl_2(aq) + H_2(g)

• Solid

• Gas

• Aqueous solution

In the chemical reaction below, if 3 mol of chlorine molecules react with excess potassium iodide, how many moles of potassium chloride are produced?

Cl₂ + 2KI --> I₂ + 2KCl

• 1.5 mol

• 6 mol

• 9 mol

True or False? "The difference between a salt's hydrated mass and its anhydrous mass is equal to the mass of its water of crystallisation"

• True

• False

Which of the following techniques would not be used to determine the formula of an anhydrous metal oxide?

• Hydration of the metal oxide

• Combustion of the metal oxide

• Reduction of the metal oxide

What is the mass of one mole of ^12₆C

• 18 g

• 6 g

• 12 g

How can you calculate the number of moles of a substance, given its mass in grams?

A formula that gives the smallest whole number ratio of atoms in a compound is...

• ...the empirical formula.

• ...the molecular formula.

• ...the relative formula.