4. Suppose that an excess of propane, C3H8 , burns in 320 g of oxygen, How many moles of water will be formed?

molar mass of O₂ is 32 g

5 moles O₂ yields 4 moles H₂O

5:4=320:x,so 5x=1280 therefore x =256mol of water

You didn't convert 320 g O2 to mols first.

mols O2 = 320/32 = 10; then
10 x 5/4 = 8.00 mols H2O formed.

8.0 moles

4.0 moles

18.75 mol H2O

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