What volume of propane is burnt for every `100 " cm"^(3)` of oxygen used in the reaction `C_(3)H_(8) + 5O_(2) to 3CO_(2) + 4H_(2)O`? Gas volumes are measured under the same conditions.

Explanation

To solve the problem of determining the volume of propane burnt for every 100 cm³ of oxygen used in the combustion reaction of propane, we can follow these steps:

### Step-by-Step Solution:

1. **Write the Balanced Chemical Equation**:
The balanced equation for the combustion of propane (C₃H₈) is:
\[ C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O \]
This equation shows that 1 volume of propane reacts with 5 volumes of oxygen.

2. **Identify the Volume Ratio**:
From the balanced equation, we can see that:
- 1 volume of C₃H₈ (propane) reacts with 5 volumes of O₂ (oxygen).
- Therefore, the ratio of propane to oxygen is 1:5.

3. **Calculate the Volume of Propane for 100 cm³ of Oxygen**:
If we have 100 cm³ of oxygen, we can set up a proportion based on the ratio:
\[ \text{Volume of Propane} = \frac{1 \text{ volume of propane}}{5 \text{ volumes of oxygen}} \times 100 \text{ cm}^3 \]
\[ \text{Volume of Propane} = \frac{1}{5} \times 100 \text{ cm}^3 = 20 \text{ cm}^3 \]

4. **Conclusion**:
Therefore, for every 100 cm³ of oxygen used, 20 cm³ of propane is burnt.

### Final Answer:
The volume of propane burnt for every 100 cm³ of oxygen used is **20 cm³**.

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