Reactant Chemistry Example 4

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Example 4

hard
A student mixes 5.05.0 g of sodium (Na\text{Na}) with excess water. The reaction is: 2Na+2H2O→2NaOH+H22\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2. Calculate the mass of the reactant sodium consumed and the moles of H2\text{H}_2 produced. (Na = 23.0 g/mol23.0\,\text{g/mol})

Solution

  1. 1
    All 5.05.0 g of sodium is consumed since water is in excess. Moles of Na =5.023.0=0.217 mol= \frac{5.0}{23.0} = 0.217\,\text{mol}.
  2. 2
    From the equation, 2 moles of Na produce 1 mole of H2\text{H}_2. So moles of H2=0.2172=0.109 mol\text{H}_2 = \frac{0.217}{2} = 0.109\,\text{mol}.
  3. 3
    The reactant Na is the limiting reactant here, determining the amount of product formed.

Answer

5.0 g Na consumed,  0.109 mol H2 produced5.0\,\text{g Na consumed},\; 0.109\,\text{mol H}_2\text{ produced}
When one reactant is in excess, the other reactant (sodium in this case) is completely consumed and determines the maximum amount of product. This is the concept of the limiting reactant.

About Reactant

A starting substance that is consumed and chemically transformed during a chemical reaction, appearing on the left side of a chemical equation before the reaction.

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More Reactant Examples

Example 1 easy

Define the term 'reactant' in a chemical reaction. In the reaction [formula], identify all reactants

Example 2 medium

In the reaction [formula], identify the reactants and determine the mole ratio in which they react.

Example 3 medium

In the combustion of propane, [formula], how many moles of [formula] are needed to react completely

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