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Answer:
0.63 moles of water
Step-by-step explanation:
The equation of the reaction is;
C8H18(g) + 25/2 O2(g) --------> 8CO2(g) + 9H2O(l)
If 1 mole of octane yields 9 moles of water
0.070 mol of octane will yield 0.070 * 9/1 = 0.63 moles of water
Hence, 0.070 moles of octane yields 0.63 moles of water.