Write the molecular equation for the reactions of phosphoric acid with calcium.

H3PO4 + Ca —> Ca3 (PO4) 2 + H2. It turns out calcium phosphate and hydrogen H.

The chemical reaction must be equalized by arranging the coefficients. It is necessary that the number of atoms of substances on the left side be equal to the number of atoms of the same substances on the right side.

There are 3 hydrogen atoms H on the left, and 2. On the right, we put two in front of H3PO4, and three in front of H2 to equalize the number of hydrogen atoms H:

2H3PO4 + Ca —> Ca3 (PO4) 2 + 3H2.

The number of phosphorus atoms P on the left and on the right is equal, two atoms each.

The number of oxygen atoms O left and right is equal, eight atoms each.

Calcium atoms Ca differs on the left and right, on the left – one atom, and on the right – three atoms. Therefore, before Ca on the left, you need to put a three in order to equalize:

2H3PO4 + 3Ca —> Ca3 (PO4) 2 + 3H2.

This is the final reaction with the odds in place.

Answer: 2H3PO4 + 3Ca —> Ca3 (PO4) 2 + 3H2.