Calculate the mass of the oxide obtained by the interaction of 4 g of calcium and 4 g of oxygen.

Given:

m (Ca) = 4 g

m (O2) = 4 g

To find:

m (CaO) -?

Decision:

1) We compose the reaction equation corresponding to the condition of the problem:

2Ca + O2 = 2CaO;

2) Find the amount of calcium and oxygen:

n (Ca) = m: M = 4 g: 40 g / mol = 0.1 mol

n (O2) = m: M = 4 g: 32 g / mol = 0.125 mol

We use a lower value for calculations to get more accurate calculations. We work with Ca:

3) We compose logical equality:

if 2 mol Ca gives 2 mol CaO,

then 0.1 mol Ca will give x mol CaO,

then x = 0.1 mol.

4) We find the mass of calcium oxide obtained during the reaction:

m (CaO) = n * M = 0.1 mol * 56 g / mol = 5.6 g;

Answer: m (CaO) = 5.6 g.