Calculate the change in free energy when you drop 4.70 g of calcium metal into a beaker containing excess water so that Ca(OH)2(s) and H2 gas are formed? The delta-G values you need are in your textbook. The units are kJ.
dGorxn = (n*dGo formation products) - (n*dGo formation reactants) gives you the dG for the reaction. Call that Y.
Then dG for 4.70 g Ca will be
Y kJ/mol x (# mols Ca in 4.70g) = ?
You may want to write and balance the equation.