To determine the volume of oxygen needed for the complete combustion of 3.3 dm³ of propane (C₃H₈) at STP (Standard Temperature and Pressure), we can use the stoichiometry of the given balanced chemical equation:
\[ \text{C}_3\text{H}_8 + 5\text{O}_2 \rightarrow 3\text{CO}_2 + 4\text{H}_2\text{O} \]
From the balanced equation, we see that 1 mole of propane reacts with 5 moles of oxygen.
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Find the volume ratio: At STP, 1 mole of any gas occupies 22.4 dm³. Therefore, the volume ratios of gases can be used directly from the coefficients in the balanced equation.
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Volume of O₂ needed: Since 1 volume of propane requires 5 volumes of oxygen, if we have 3.3 dm³ of propane, the volume of oxygen required can be calculated as follows:
\[ \text{Volume of } O_2 = \text{Volume of } C_3H_8 \times \frac{5 \text{ mol O}_2}{1 \text{ mol C}_3\text{H}_8} \]
\[ \text{Volume of } O_2 = 3.3 , \text{dm}^3 \times 5 = 16.5 , \text{dm}^3 \]
Thus, the volume of oxygen needed for the complete combustion of 3.3 dm³ of propane at STP is 16.5 dm³.
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