Quick questions on Formulae and chemical equations: N(A)-Level Chemistry

To write the formula of an ionic compound, balance the charges so the compound is neutral:

When more than one of a group ion is needed, put it in brackets with a subscript. For example, calcium hydroxide is $\text{Ca(OH)}_2$, because one $\text{Ca}^{2+}$ needs two $\text{OH}^{-}$ ions.

A word equation names the reactants and products with an arrow:

A symbol equation uses formulae. To balance it, put big numbers (coefficients) in front of formulae until each element has equal atoms on both sides. Never change a formula; only change the numbers in front. Then add state symbols:

Write the formula of aluminium oxide, given the ions $\text{Al}^{3+}$ and $\text{O}^{2-}$. [2 marks]

Balance the equation $\text{Fe} + \text{O}_2 \rightarrow \text{Fe}_2\text{O}_3$. [2 marks]

Write the balanced symbol equation, with state symbols, for zinc reacting with hydrochloric acid to give zinc chloride solution and hydrogen gas. [2 marks]