Question

The chloride of a metal has the formula $MC{l_3}$. The formula of its phosphate will be :
a.) ${M_2}P{O_4}$
b.) $MP{O_4}$
c.) ${M_3}P{O_4}$
d.) $M{(P{O_4})_2}$

Answer 1

Hint: We have been given the formula of metal chloride. From that, we can find the valency of the metal atom. We know that the phosphate ion has an overall charge of -3. So, by cross multiplying the valencies, we can find out the molecular formula of metal phosphate.

Complete Solution :
In such a type of question, let us first see what is given to us and then we will derive the answer.
We are given that the chloride of the metal has the formula = $MC{l_3}$
We know that the Cl atom has valency = -1.
So, the three Cl atoms will have = -3

Thus, as the molecule is neutral overall. So, the metal will have a positive charge equal to the total negative charge of three Cl atoms.
- So, metal will have valency = +3
- Further, we know that one phosphate ion has an overall charge of = -3
- So, one phosphate ion will combine with one metal atom and form the molecule as -
$MP{O_4}$.
So, the correct answer is “Option B”.

Note: It must be noted that phosphate ion like carbonate ion has an overall charge of -3. The phosphate ion consists of one phosphorus atom attached to four oxygen atoms. The three oxygen atoms have a charge of -1 each. Thus, the overall charge on the ion is -3.