Mass O2 32 g Calculate the mass of calcium.

Given:
m (O2) = 32 g

To find:
m (Ca) -?

Decision:
1) Write the equation of a chemical reaction:
2Ca + O2 => 2CaO;
2) Calculate the molar masses of O2 and Ca:
M (O2) = Mr (O2) = Ar (O) * 2 = 16 * 2 = 32 g / mol;
M (Ca) = Mr (Ca) = Ar (Ca) = 40 g / mol;
3) Calculate the amount of substance O2:
n (O2) = m (O2) / M (O2) = 32/32 = 1 mol;
4) Determine the amount of Ca substance (taking into account the coefficients in the reaction equation):
n (Ca) = n (O2) * 2 = 1 * 2 = 2 mol;
5) Calculate the mass of Ca:
m (Ca) = n (Ca) * M (Ca) = 2 * 40 = 80 g.

Answer: Ca mass is 80 g.