Aluminium metal replaces iron from iron oxide $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$giving aluminium oxide and iron. Which is more reactive; aluminium or iron?

Consider the general reaction:

${\mathrm{A}}^{2+} + {\mathrm{B}}^{2-} \to \mathrm{A} + \mathrm{B}$

Name the reducing agent.

Identify the type of reaction in the following example:

${\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right) +{\mathrm{BaCl}}_2\left(\mathrm{aq}\right) \to {\mathrm{BaSO}}_4\left(\mathrm{s}\right) +2\mathrm{NaCl}\left(\mathrm{aq}\right)$

Identify the type of reaction in the following example:

$2{\mathrm{H}}_2\left(\mathrm{g}\right) +{\mathrm{O}}_2\left(\mathrm{g}\right) \to 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Balance the given chemical equation:

${\mathrm{HNO}}_3 +\mathrm{Ca}{\left(\mathrm{OH}\right)}_2 \to \mathrm{Ca}{\left({\mathrm{NO}}_3\right)}_2 +{\mathrm{H}}_2\mathrm{O}$

Balance the following equations:

$$\begin{gathered} {\mathrm{CH}}_4\left(\mathrm{g}\right) +{\mathrm{O}}_2\left(\mathrm{g}\right) \to {\mathrm{CO}}_2\left(\mathrm{g}\right) +{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Al}\left(\mathrm{s}\right) +\mathrm{HCl}\left(\mathrm{aq}\right) \to {\mathrm{AlCl}}_3\left(\mathrm{aq}\right) +{\mathrm{H}}_2\left(\mathrm{g}\right) \end{gathered}$$

What is meant by a chemical equation? What do the symbols g, l, aq and $\rightleftharpoons$signify in the following equation?

${\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)$