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===Examples===
2H<sub>2</sub> (g) + O<sub>2</sub> (g) → 2H<sub>2</sub>O(l)
C<sub>2</sub>H<sub>4</sub> (g) + Br<sub>2</sub> (g) → C<sub>2</sub>H<sub>4</sub>Br<sub>2</sub>(g)
C<sub>6</sub>H<sub>12</sub>O<sub>6</sub> (s) + 6O<sub>2</sub> (g) → 6H<sub>2</sub>O (l) + 6CO<sub>2</sub>(g)
4Al (s) + 3O<sub>2</sub> (g) → 2Al<sub>2</sub>O<sub>3</sub>(s) ===Calculating the Mass Required for a Complete Reaction==={| class="wikitable"| style="height:20px; width:200px; text-align:center;" |Find the [[mass]] of [[Oxygen]] needed to completely [[oxidise]] all of the [[Magnesium]]: 2Mg + O<sub>2</sub> → 2MgO 48g + x = y | style="height:20px; width:200px; text-align:center;" |Find the [[mass]] of [[Oxygen]] needed for the [[Complete Combustion|complete combustion]] of [[Methane]]. CH<sub>4</sub> + 2O<sub>2</sub> → 2H<sub>2</sub>O + CO<sub>2</sub> 32g + x = y | style="height:20px; width:200px; text-align:center;" |Find the [[mass]] of [[Hydrochloric Acid]] needed to completely [[Neutralise (Chemistry)|neutralise]] all of the [[Sodium Hydroxide]]. NaOH + HCl → NaCl + H<sub>2</sub>O 20g + x = y + z|-| style="height:20px; width:200px; text-align:center;" |Find the [[Relative Formula Mass]] of the [[reactant]]s. M<sub>r</sub> of Mg = 24g M<sub>r</sub> of O<sub>2</sub> = 16x2 M<sub>r</sub> of O<sub>2</sub> = 32g | style="height:20px; width:200px; text-align:center;" |Find the [[Relative Formula Mass]] of the [[reactant]]s. M<sub>r</sub> of CH<sub>4</sub> = 16g M<sub>r</sub> of O<sub>2</sub> = 16x2 M<sub>r</sub> of O<sub>2</sub> = 32g | style="height:20px; width:200px; text-align:center;" |Find the [[Relative Formula Mass]] of the [[reactant]]s. M<sub>r</sub> of NaOH = 40g M<sub>r</sub> of HCl = 36.5g |-| style="height:20px; width:200px; text-align:center;" |State the [[ratio]] of [[mole]]s of each [[chemical]] needed. 2 [[mole]]s of Mg are needed for every 1 [[mole]] of O<sub>2</sub> | style="height:20px; width:200px; text-align:center;" |State the [[ratio]] of [[mole]]s of each [[chemical]] needed. 1 [[mole]] of CH<sub>4</sub> is needed for every 2 [[mole]]s of O<sub>2</sub> | style="height:20px; width:200px; text-align:center;" |State the [[ratio]] of [[mole]]s of each [[chemical]] needed. 1 [[mole]] of HCl are needed for every 1 [[mole]] of NaOH |- | style="height:20px; width:200px; text-align:center;" |Find the number of [[mole]]s supplied of the known [[mass]]. No. [[Mole]]s = <math>\frac{Mass}{M_r}</math> No. [[Mole]]s = <math>\frac{48}{24}</math> No. [[Mole]]s = 2 Mole Therefore 1 [[mole]] of O<sub>2</sub> is needed. 1 [[mole]] of O<sub>2</sub> = 32g | style="height:20px; width:200px; text-align:center;" |Find the number of [[mole]]s supplied of the known [[mass]]. No. [[Mole]]s = <math>\frac{Mass}{M_r}</math> No. [[Mole]]s = <math>\frac{32}{16}</math> No. [[Mole]]s = 2 Mole Therefore 4 [[mole]]s of O<sub>2</sub> are needed. 4 [[mole]]s of O<sub>2</sub> = 128g | style="height:20px; width:200px; text-align:center;" |Find the number of [[mole]]s supplied of the known [[mass]]. No. [[Mole]]s = <math>\frac{Mass}{M_r}</math> No. [[Mole]]s = <math>\frac{20}{40}</math> No. [[Mole]]s = 0.5 Mole Therefore 0.5 [[mole]] of HCl is needed. 0.5 [[mole]] of HCl = 18.25g |}
===Balancing Equations===