Question

16.7 grams of chlorine gas are allowed to react with with 3.31 grams of water
What is the maximum amount of hydrochloric acid that can be formed in grams

Answer 1

For the following reaction, 20.8 grams of iron are allowed to react with with 4.82 grams of oxygen gas.

iron (s) + oxygen (g) iron(II) oxide (s)

What is the maximum amount of iron(II) oxide that can be formed? grams

What is the FORMULA for the limiting reagent?

What amount of the excess reagent remains after the reaction is complete? grams

Answer 2

For the first one, you have a stoichiometry problem. Here is a solve example. Just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html

For the second one, this is a limiting reagent problem. You know that because BOTH (and not just one) of the reactants are given. What you do is to solve two stoichiometry problems, just as in your first one, then use the one producing the smaller value. The reagent producing the smaller value will be the limiting reagent; take that one, convert to moles of the non-limiting reagent, and subtract from the initial amount.