# Chapter 4 - Exercises - Page 186: 25

The balanced equation is: $2C_6H_{14}(g) + 19O_2(g) -- \gt 12CO_2(g) + 14H_2O(g)$ The number of moles of oxygen gas that are required to react completely with 7.2 moles of hexane is equal to 68 moles $(O_2)$.

#### Work Step by Step

1. Balance the equation: - Start by balancing the number of carbons: $C_6H_{14}(g) + O_2(g) -- \gt 6CO_2(g) + H_2O(g)$ - Balance the number of hydrogens: $C_6H_{14}(g) + O_2(g) -- \gt 6CO_2(g) + 7H_2O(g)$ - There is a total of 6*2 + 7 = 19 oxygens on the products side, so: $C_6H_{14}(g) + \frac{19}{2}O_2(g) -- \gt 6CO_2(g) + 7H_2O(g)$ Multiply all the coefficients by 2: $2C_6H_{14}(g) + 19O_2(g) -- \gt 12CO_2(g) + 14H_2O(g)$ 2. Now, use the coefficients to calculate the number of moles $(O_2)$. $7.2 moles (C_6H_{14}) \times \frac{19 mol(O_2)}{2mol(C_6H_{14})} = 68\ moles (O_2)$

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