Thanks for that brenton, i think i've got those types of questions down pat :)
However i'm not quite sure on some other ones like these:
1) CO(g) reacts with H<sub>2</sub> to form CO<sub>2</sub>(g) and H<sub>2</sub>(g) What is the percentage yield if 1.8g H<sub>2</sub>(g) gas is formed...