Given the reaction: ca + 2h2o → ca(oh)2 + h2 what is the total number of moles of ca needed to react completely with 4.0 moles of h2o?

Since the given equation is balanced, we know the Ca and the H2O are in a 1:2 ratio (to see the ratio, look at the coefficients in front of the molecules). Then, there are a few different ways to solve the problem. I am going to show you how to solve it using a ratio of moles of Ca/moles of H2O: x/1=4/2. First, you cross multiply to get 2x=4. Then, you divide both sides by 2 to get x=2 moles of Ca.

What are the statements?