Grams (Mass) Chemistry Example 4

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Example 4

hard
In the reaction 2Al+3Cl2→2AlCl32\text{Al} + 3\text{Cl}_2 \rightarrow 2\text{AlCl}_3, calculate the mass in grams of AlCl3\text{AlCl}_3 produced from 13.513.5 g of aluminum reacting with excess chlorine. (Al = 26.9826.98, Cl = 35.45 g/mol35.45\,\text{g/mol})

Solution

  1. 1
    Moles of Al =13.526.98=0.500 mol= \frac{13.5}{26.98} = 0.500\,\text{mol}.
  2. 2
    Mole ratio: 2 mol Al → 2 mol AlCl3\text{AlCl}_3 (1:1). So moles of AlCl3=0.500 mol\text{AlCl}_3 = 0.500\,\text{mol}.
  3. 3
    Molar mass of AlCl3=26.98+3(35.45)=133.33 g/mol\text{AlCl}_3 = 26.98 + 3(35.45) = 133.33\,\text{g/mol}. Mass =0.500×133.33=66.7 g= 0.500 \times 133.33 = 66.7\,\text{g}.

Answer

66.7 g of AlCl366.7\,\text{g of AlCl}_3
Stoichiometric mass-to-mass conversions always require three steps: grams of reactant → moles of reactant → moles of product (via mole ratio) → grams of product. The molar mass is used at both conversion points.

About Grams (Mass)

A gram (g) is the fundamental unit of mass in chemistry, defined as one thousandth of a kilogram.

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Example 1 easy

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Example 2 medium

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Example 3 medium

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Related Concepts

MoleMolar Mass