Question

By the reaction between

H3PO4 and Ca(OH)2,
Can be formede:

a. Ca(HPo4)2,
b. СaHP4
c. Ca(H2PO4)2
d. Ca2HP02
e.Сa3(PO4)2

the correct answers : b, c, e

the question is:
I am preparing for an admittion test in chemistry, I face this kind of questions which I dont how to understand or if I should only memorize.

I appreciate all your help.
thank you alot.​

Answer 1

First step is to find what the products would be. Since this seems to be a double displacement, you get: H3PO4(aq)+Ca(OH)2(aq)→ H2O(L)+Ca3(PO4)2(s)

You know the products because H has a charge of +1, so PO4 must have a charge of -3, and since OH has a charge of -1, Ca must be +2. Then make each compound have a net charge of 0. H20 is a liquid since aq solutions have liquid water. Ca3(PO4)2 is a solid, use the solubility rules.

Lastly, balance the equation: 2H3PO4(aq)+3Ca(OH)2(aq)→ 6H2O(L)+Ca3(PO4)2(s)

So the salt formed is Ca3(PO4)2

Answer 2

ANSWER is E

Step-by-step explanation:

2H₃PO₄ + 3Ca(OH)₂→ 6H₂O + Ca₃(PO₄)₂