The combustion of hexane (C6H14), a component of gasoline, is represented by the balanced chemical equation: 2 C6H14(I) + 19 O2(g) ® 12 CO2(g) + 14 H2O(g). If 1.0 mole of hexane undergoes combustion, moles of O2 are required.
a. 19 moles
b. 7 moles
c. 9.5 moles
d. 26 moles
e. 21 moles
The Correct Answer and Explanation is :
The correct answer is c. 9.5 moles.
Explanation:
The balanced chemical equation for the combustion of hexane is: 2C6H14(l)+19O2(g)→12CO2(g)+14H2O(g)2 C_6H_{14}(l) + 19 O_2(g) \rightarrow 12 CO_2(g) + 14 H_2O(g)
This equation tells us that 2 moles of hexane react with 19 moles of oxygen gas (O₂). The relationship between hexane and oxygen is a 2:19 ratio.
To determine the amount of oxygen needed for 1 mole of hexane, we use a proportion: 19 moles of O22 moles of C6H14=X moles of O2/1 mole of C6H14\frac{19 \text{ moles of } O_2}{2 \text{ moles of } C_6H_{14}} = X \text{ moles of } O_2 / 1 \text{ mole of } C_6H_{14}
Solving for XX: X=192=9.5 moles of O2X = \frac{19}{2} = 9.5 \text{ moles of } O_2
Why is this the correct answer?
- The reaction follows the law of conservation of mass, meaning the number of atoms of each element must be the same on both sides.
- The balanced equation indicates that 2 moles of C₆H₁₄ require 19 moles of O₂.
- If we reduce this proportion to 1 mole of C₆H₁₄, the required amount of oxygen is 9.5 moles.
Why are the other choices incorrect?
- 19 moles (option a) is the amount needed for 2 moles of hexane.
- 7 moles (option b) is not derived from the correct ratio.
- 26 moles (option d) is too high.
- 21 moles (option e) does not match the correct proportion.
Thus, the correct answer is 9.5 moles of O₂, which corresponds to option c.