In order to convert between mols of compounds, you need to use the mole ratio. First, divide 2.5 moles of oxygen gas by 8 moles of oxygen because that is the number of moles of oxygen gas in the balanced equation. Then to find the number of moles of carbon dioxide, multiply by the 5 moles of carbon dioxide in the mole ratio. After multiplying, you get the answer 1.56 moles of carbon dioxide and with 2 significant figures present you would round to 1.6 moles.
