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==Key Stage 4==
===Meaning===
===About Yield===
: The theoretical '''yield''' of [[product]] form a [[Chemical Reaction|chemical reaction]] can be calculated using the [[Balanced Symbol Equation|balanced symbol equation]] and the [[Relative Formula Mass|relative formula masses]] of all the [[molecule]]s involved.
: The experimental '''yield''' from a [[Chemical Reaction|chemical reaction]] is often not as large as the theoretical '''yield''' because not all of the [[reactant]]s will [[Chemical Reaction|react]]. This experimental '''yield''' is often expressed as a [[percentage]] of the theoretical '''yield''' and is known as the [[Percentage Yield]].
===Examples===
{| class="wikitable"
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Calculate the '''yield''' of [[Magnesium Oxide]] given 48g of [[Magnesium]] and excess [[Oxygen]].| style="height:20px; width:200px; text-align:center;" |
Find the '''yield''' of [[Carbon Dioxide]] when 32g of [[Methane]] [[Chemical reaction|reacts]] with excess [[Oxygen]].
| style="height:20px; width:200px; text-align:center;" |
Find the '''yield''' of [[Sodium Chloride]] when 80g of [[Sodium Hydroxide]] [[Chemical Reaction|react]] with 73g of [[Hydrochloric Acid]].
|-
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'''Write the Balanced Symbol Equation'''
2Mg + O<sub>2</sub> → 2MgO
| style="height:20px; width:200px; text-align:center;" |
'''Write the Balanced Symbol Equation'''
CH<sub>4</sub> + 2O<sub>2</sub> → 2H<sub>2</sub>O + CO<sub>2</sub>
| style="height:20px; width:200px; text-align:left;" |
'''Write the Balanced Symbol Equation'''
NaOH + HCl → NaCl + H<sub>2</sub>O
|-
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Find the [[Relative Formula Mass]] of the [[reactant]]s and [[product]]s.
M<sub>r</sub> of Mg = 24g
M<sub>r</sub> of 2Mg = 48g
M<sub>r</sub> of O<sub>2</sub> = 16x2
M<sub>r</sub> of O<sub>2</sub> = 32g
M<sub>r</sub> of MgO = 24+16
M<sub>r</sub> of MgO = 40g
| style="height:20px; width:200px; text-align:left;" |
Find the [[Relative Formula Mass]] of the [[reactant]]s and [[product]]s.
M<sub>r</sub> of CH<sub>4</sub> = 12+1x4
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
M<sub>r</sub> of 2O<sub>2</sub> = 64g
M<sub>r</sub> of CO<sub>2</sub> = 12+16x2
M<sub>r</sub> of CO<sub>2</sub> = 44g
M<sub>r</sub> of H<sub>2</sub>O = 1x2+16
M<sub>r</sub> of H<sub>2</sub>O = 18
M<sub>r</sub> of 2H<sub>2</sub>O = 36g
| style="height:20px; width:200px; text-align:left;" |
Find the [[Relative Formula Mass]] of the [[reactant]]s and [[product]]s.
M<sub>r</sub> of NaOH = 40g
M<sub>r</sub> of HCl = 36.5g
M<sub>r</sub> of NaCl = 23+35.5
M<sub>r</sub> of NaCl = 58.5g
M<sub>r</sub> of H<sub>2</sub>O = 1x2+16
M<sub>r</sub> of H<sub>2</sub>O = 18
|-
| style="height:20px; width:200px; text-align:left;" |
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:left;" |
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:left;" |
State the [[ratio]] of [[mole]]s of each [[chemical]] needed.
1 [[mole]] of HCl are needed for every 1 [[mole]] of NaOH
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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:left;" |
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:left;" |
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
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