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===Example Calculations===
 
===Example Calculations===
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{| class="wikitable"
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| style="height:20px; width:300px; text-align:center;" |
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Calculate the '''atom economy''' for [[product|producing]] [[Ammonia]] in the following [[Chemical Reaction|reaction]]:
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N<sub>2</sub>(g) + 3H<sub>2</sub>(g) ⇌ 2NH<sub>3</sub>(g)
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| style="height:20px; width:300px; text-align:center;" |
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Calculate the '''atom economy''' for [[product|producing]] [[Calcium Oxide]] in the following [[Chemical Reaction|reaction]]:
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CaCO<sub>3</sub>(s) → CaO(s) + CO<sub>2</sub>(g)
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| style="height:20px; width:300px; text-align:center;" |
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Calculate the '''atom economy''' for [[product|producing]] [[Sodium Chloride]] in the following [[Chemical Reaction|reaction]]:
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HCl(aq) + NaOH(aq) → NaCl(aq) + H<sub>2</sub>O(l)
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|-
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the [[Relative Formula Mass]] of the relevant [[reactant]]s and [[product]].'''
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M<sub>r</sub> of N<sub>2</sub> = 28g
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M<sub>r</sub> of H<sub>2</sub> = 2g
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M<sub>r</sub> of NH<sub>3</sub> = 17g
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the [[Relative Formula Mass]] of the relevant [[reactant]]s and [[product]].'''
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M<sub>r</sub> of CaCO<sub>3</sub> = 100g
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M<sub>r</sub> of CaO = 56g
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the [[Relative Formula Mass]] of the relevant [[reactant]]s and [[product]].'''
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M<sub>r</sub> of HCl = 36.5g
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M<sub>r</sub> of NaOH = 40g
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M<sub>r</sub> of NaCl = 58.5g
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|-
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the total [[mass]] of [[reactant]]s needed and the total [[mass]] of the desired [[product]].'''
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Mass of Reactants = 28 + 3 x 2
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Mass of Reactants = 34g
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Mass of desired Product = 2 x 17
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Mass of desired Product = 34g
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the total [[mass]] of [[reactant]]s needed and the total [[mass]] of the desired [[product]].'''
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Mass of Reactants = 100g
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Mass of desired Product = 56g
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the total [[mass]] of [[reactant]]s needed and the total [[mass]] of the desired [[product]].'''
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Mass of Reactants = 36.5 + 40
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Mass of Reactants = 76.5g
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Mass of desired Product = 58.5g
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|-
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the number of [[mole]]s supplied of the known [[mass]].'''
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No. [[Mole]]s = <math>\frac{Mass}{M_r}</math>
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No. [[Mole]]s = <math>\frac{48}{24}</math>
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No. [[Mole]]s = 2 mol
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Therefore 2 [[mole]]s of MgO is produced.
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2 [[mole]]s of MgO = 40x2
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'''Yield''' = 80g
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the number of [[mole]]s supplied of the known [[mass]].'''
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No. [[Mole]]s = <math>\frac{Mass}{M_r}</math>
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No. [[Mole]]s = <math>\frac{320}{16}</math>
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No. [[Mole]]s = 20 mol
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Therefore 40 [[mole]]s of H<sub>2</sub>O are produced.
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40 [[mole]]s of CO<sub>2</sub> = 18x40
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'''Yield''' = 720g
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| style="height:20px; width:300px; text-align:left;" |
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'''Find the number of [[mole]]s supplied of the known [[mass]].'''
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No. [[Mole]]s = <math>\frac{Mass}{M_r}</math>
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No. [[Mole]]s = <math>\frac{7.3}{36.5}</math>
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No. [[Mole]]s = 0.2 mol
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Therefore 0.2 [[mole]] of [[Sodium Chloride]] is produced.
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0.2 [[mole]] of NaCl = 11.7g
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'''Yield''' = 11.7g
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|}

Revision as of 19:42, 27 January 2019

Key Stage 4

Meaning

Atom Economy is the percentage of atoms in the reactants which ends up in the desired products.

About Atom Economy

During a chemical reaction there is often more than one product. When there is more than one product often one is desired and one is a waste product that must be disposed of.
To reduce costs and increase the efficiency of a process chemical engineers design systems that produce the maximum amount of a desired product and a minimum amount of waste products.

Atom Economy Equation

Percentage Atom Economy = [(Relative Formula Mass of Desired Product)/(Sum of Relative Formula Masses of Reactants)] x 100%

% Atom Economy = \(frac{M_desiredproduct}{M_allreactants}\)

Where:

Mdesiredproduct = Relative Formula Mass of Desired Product

Mallreactants = Sum of Relative Formula Masses of Reactants

Example Calculations

Calculate the atom economy for producing Ammonia in the following reaction: N2(g) + 3H2(g) ⇌ 2NH3(g)

Calculate the atom economy for producing Calcium Oxide in the following reaction: CaCO3(s) → CaO(s) + CO2(g)

Calculate the atom economy for producing Sodium Chloride in the following reaction: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

Find the Relative Formula Mass of the relevant reactants and product.

Mr of N2 = 28g

Mr of H2 = 2g

Mr of NH3 = 17g

Find the Relative Formula Mass of the relevant reactants and product.

Mr of CaCO3 = 100g

Mr of CaO = 56g

Find the Relative Formula Mass of the relevant reactants and product.

Mr of HCl = 36.5g

Mr of NaOH = 40g

Mr of NaCl = 58.5g

Find the total mass of reactants needed and the total mass of the desired product.

Mass of Reactants = 28 + 3 x 2

Mass of Reactants = 34g

Mass of desired Product = 2 x 17

Mass of desired Product = 34g

Find the total mass of reactants needed and the total mass of the desired product.

Mass of Reactants = 100g

Mass of desired Product = 56g

Find the total mass of reactants needed and the total mass of the desired product.

Mass of Reactants = 36.5 + 40

Mass of Reactants = 76.5g

Mass of desired Product = 58.5g

Find the number of moles supplied of the known mass.

No. Moles = \(\frac{Mass}{M_r}\)

No. Moles = \(\frac{48}{24}\)

No. Moles = 2 mol

Therefore 2 moles of MgO is produced.

2 moles of MgO = 40x2

Yield = 80g

Find the number of moles supplied of the known mass.

No. Moles = \(\frac{Mass}{M_r}\)

No. Moles = \(\frac{320}{16}\)

No. Moles = 20 mol

Therefore 40 moles of H2O are produced.

40 moles of CO2 = 18x40

Yield = 720g

Find the number of moles supplied of the known mass.

No. Moles = \(\frac{Mass}{M_r}\)

No. Moles = \(\frac{7.3}{36.5}\)

No. Moles = 0.2 mol

Therefore 0.2 mole of Sodium Chloride is produced.

0.2 mole of NaCl = 11.7g

Yield = 11.7g

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