a mixture of .0285g of H and .0141 mol of oxygen in a closed container is sparked to initiate a reaction. How many grams of H2O can form?Which reactant is in excess and how many grams remain?

Answer 1

Write and balance the equation.
Convert g Hydrogen to moles. moles = grams/molar mass
You have oxygen in moles.
Then take one element at a time and determine the moles H2O formed. Follow the instructions on this worked example of a stoichiometry problem.
http://www.jiskha.com/science/chemistry/stoichiometry.html
Basically, you take H (and ignore oxygen) and calculate the moles H2O formed.
Then take oxygen (and ignore hydrogen) and calculate moles H2O formed.
You will obtain two different answers and only one can be right; the correct one in limiting reagent problems is ALWAYS the smaller value. Then take that value of moles and convert mole to grams. grams = moles x molar mass.
Post your work if you get stuck.