If a reaction occurs and there were 10 g of Ca reacting with 20 grams of water, and 5 grams of H2
was produced, how much Ca(OH)2 was produced?
Show your work.
Ca + H2O - Ca(OH)2 + H2

18.52g

Explanation:

(relative atomic masses: H = 1.01, O = 16.00, Ca = 40.08)

Equation (balanced):

Ca + 2H2O -> Ca(OH)2 +H2

First, calculate the number of moles of 10g calcium

No. of moles of Ca  = 10/40.08 = 0.25 mol

Then, calculate the  number of moles of 20g water

No of moles of H2O = 1.11 mol

According to the balanced equation, 1 mole of calcium reacts with 2 moles of H2O completely.  Therefore, H2O is in excess.

So, 1 mole of calcium reacts with water to form 1 mole of Ca(OH)2 (according to the mole ratio shown in the balanced equation)

Therefore, 0.25 mol of Ca(OH)2 is produced.

Mass of Ca(OH)2 produced = no. of moles x molar mass = 0.25 x (40.08 + 16 + 16 + 1.01 + 1.01) = 18.52g

Good luck!