The number of moles of oxygen gas used in the complete combustion of 1 mole of glucose is:
6
Understanding the Complete Combustion of Glucose
Complete combustion is a chemical process where a substance reacts rapidly with oxygen, usually producing heat and light. When organic compounds like glucose undergo complete combustion, the products are typically carbon dioxide (\(\text{CO}_2\)) and water (\(\text{H}_2\text{O}\)).
Balanced Chemical Equation for Glucose Combustion
To determine the amount of oxygen gas (\(\text{O}_2\)) required for the complete combustion of glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)), we need to write and balance the chemical equation for the reaction. The unbalanced equation is:
\[\text{C}_6\text{H}_{12}\text{O}_6\text{(s)} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} + \text{H}_2\text{O}\text{(l)}\]
Now, let's balance the equation:
- Start with Carbon (\(\text{C}\)): There are 6 carbon atoms in glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) on the left side. So, we need 6 molecules of carbon dioxide (\(\text{CO}_2\)) on the right side to balance the carbon atoms. \[\text{C}_6\text{H}_{12}\text{O}_6 + \text{O}_2 \rightarrow 6\text{CO}_2 + \text{H}_2\text{O}\]
- Balance Hydrogen (\(\text{H}\)): There are 12 hydrogen atoms in glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) on the left side. Water (\(\text{H}_2\text{O}\)) has 2 hydrogen atoms per molecule, so we need \(12/2 = 6\) molecules of water on the right side to balance the hydrogen atoms. \[\text{C}_6\text{H}_{12}\text{O}_6 + \text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}\]
- Balance Oxygen (\(\text{O}\)): Now count the total oxygen atoms on the right side: \(6 \times \text{O}\) in \(6\text{CO}_2\) is \(6 \times 2 = 12\) oxygen atoms. \(6 \times \text{O}\) in \(6\text{H}_2\text{O}\) is \(6 \times 1 = 6\) oxygen atoms. Total oxygen atoms on the right is \(12 + 6 = 18\). On the left side, glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) has 6 oxygen atoms. Oxygen gas (\(\text{O}_2\)) has 2 oxygen atoms per molecule. Let's say we need \(x\) molecules of \(\text{O}_2\). The total oxygen on the left is \(6 + 2x\). To balance, \(6 + 2x = 18\). \(2x = 18 - 6\) \(2x = 12\) \(x = 12 / 2 = 6\). So, we need 6 molecules of oxygen gas (\(\text{O}_2\)).
The balanced chemical equation is:
\[\text{C}_6\text{H}_{12}\text{O}_6\text{(s)} + 6\text{O}_2\text{(g)} \rightarrow 6\text{CO}_2\text{(g)} + 6\text{H}_2\text{O}\text{(l)}\]
Interpreting the Balanced Equation: Molar Ratios
The coefficients in a balanced chemical equation represent the ratio of moles of the reactants and products involved in the reaction. In the balanced equation for glucose combustion:
- The coefficient for glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) is 1 (it's not explicitly written but understood).
- The coefficient for oxygen gas (\(\text{O}_2\)) is 6.
- The coefficient for carbon dioxide (\(\text{CO}_2\)) is 6.
- The coefficient for water (\(\text{H}_2\text{O}\)) is 6.
This means that for every 1 mole of glucose that undergoes complete combustion, 6 moles of oxygen gas are consumed, and 6 moles of carbon dioxide and 6 moles of water are produced.
Answering the Question
The question asks for the number of moles of oxygen gas used in the complete combustion of 1 mole of glucose. Based on the balanced chemical equation:
\[1 \text{ mole of } \text{C}_6\text{H}_{12}\text{O}_6 \text{ reacts with } 6 \text{ moles of } \text{O}_2\]
Therefore, 6 moles of oxygen gas are used.
| Substance | Coefficient | Moles in Reaction |
|---|---|---|
| Glucose (\(\text{C}_6\text{H}_{12}\text{O}_6\)) | 1 | 1 mole |
| Oxygen (\(\text{O}_2\)) | 6 | 6 moles |
| Carbon Dioxide (\(\text{CO}_2\)) | 6 | 6 moles |
| Water (\(\text{H}_2\text{O}\)) | 6 | 6 moles |
Revision Table: Key Concepts
| Concept | Explanation |
|---|---|
| Complete Combustion | Reaction with oxygen producing \(\text{CO}_2\) and \(\text{H}_2\text{O}\) for organic compounds. |
| Balanced Equation | Shows the correct proportions (moles) of reactants and products. |
| Stoichiometry | The study of the quantitative relationships between reactants and products in a chemical reaction. Coefficients in the balanced equation provide molar ratios. |
Additional Information: Biological Relevance
The complete combustion of glucose is a key process in biological systems, known as cellular respiration. In our bodies, glucose reacts with oxygen to produce energy (ATP), carbon dioxide, and water. While this biological process involves many intermediate steps and enzymes, the overall stoichiometry matches the chemical combustion equation.
The reaction releases energy, which is why glucose is a primary source of fuel for living organisms.
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