Answer: Ionic formula will be
.
Explanation:
and
ions will form a ionic compound. Ionic compounds have both metals and non-metals.
Here
is a metal and
is a non-metal.
The net charge on any compound must be 0.
So we need 2 phosphate ions to balance the charge on
ions. Similarly we need 3 Magnesium ions to balance the charge on
ions.
Criss-crossing the charges, we will get the formula as 
Criss-crossing is shown in the image below.
<span>a pure substance that can be separated into different elements by chemical means</span>
The rate of the backward reaction increases
Explanation:
It is evident that if the reaction is left to proceed spontaneously, the forward reaction is favored because it results in a decrease in pressure in the system (The total reactants have 5 moles and the products have 3 in total).
Increasing H₂O concentration is then reaction, therefore, stymies the forward reaction and favors the reserves reaction. This is because the reverse reaction will lead to reduced pressure.