Butane and Oxygen Combustion: Determining Excess Water Production

When butane undergoes combustion, a significant amount of water can be produced. The goal of this article is to explore the process behind this reaction and determine how much excess water is produced when 20.0 grams of butane react with 20.0 grams of oxygen. Understanding this will help us identify the limiting reactant and the amount of water formed.

Combustion Reaction and Balanced Equation

The balanced chemical equation for the combustion of butane (C4H10) with oxygen (O2) is given as:

2 C4H10 13 O2 → 8 CO2 10 H2O

This equation indicates that 2 moles of butane react with 13 moles of oxygen to produce 10 moles of water.

Step 1: Calculate Moles of Reactants

First, we need to convert the given masses of butane and oxygen into moles.

Molar mass 4 × 12.01 10 × 1.008 58.12 g/mol

Moles of butane 20.0 g / 58.12 g/mol ≈ 0.344 mol

Molar mass 2 × 16.00 32.00 g/mol

Moles of oxygen 20.0 g / 32.00 g/mol ≈ 0.625 mol

Step 2: Determine the Limiting Reactant

Based on the balanced equation, 2 moles of butane require 13 moles of oxygen. To find out how many moles of oxygen are needed for 0.344 moles of butane:

Moles of oxygen required 0.344 mol C4H10 × (13 mol O2 / 2 mol C4H10) ≈ 2.238 mol O2

Since we only have 0.625 moles of oxygen, oxygen is the limiting reactant.

Step 3: Calculate Water Produced

Now that we know the limiting reactant is oxygen, we can calculate the amount of water produced based on the given moles of oxygen:

Moles of water produced 0.625 mol O2 × (10 mol H2O / 13 mol O2) ≈ 0.481 mol H2O

Step 4: Convert Moles of Water to Grams

The molar mass of water (H2O) is 2 × 1.008 16.00 18.016 g/mol.

Grams of water produced 0.481 mol H2O × 18.016 g/mol ≈ 8.669 grams

Conclusion

Given that oxygen is the limiting reactant, no excess water is formed as all the produced water comes from this reaction. If you are interested in calculating the excess amount of butane left over, you can easily do so based on the initial amount of butane and the amount consumed in the reaction.

Keywords: butane combustion, oxygen, water production, limiting reactant