Question

Based on the equation below , how many moles of carbon monoxide (CO) are needed to react completely with 1.75 moles of iron (lll) oxide (Fe2O3)

Fe2O3(s) + 3CO(g) --->2Fe(s) + 3CO2(g)

Answer 1

This uses ratios, so it only has a couple of steps. First off, your reaction. It's \[1Fe _{2}O_{3}(s) + 3CO(g) \rightarrow 2Fe(s) + 3CO_{2}(g)\]As you can deduce by the reaction itself, its ratios are 1 to 3 to 2 to 3 (1:3:2:3).
What this means, is that if you have 1 mole of the first input product, you'll need 3 moles of the other input product to make this reaction work and have the desired output.
If you have 1.75 moles of the first input product and want it to react completely with the second input, you'll need 5,25 ( \[1,75*3=5,25\] ) moles of carbon mono-oxide.

This was my first answer on this site, and I hope it helped you. There might be several terms that I misused slightly, or completely for that matter, as I'm not a native english speaker.