# How do phosphate salts react with hydrochloric acid?

Jan 12, 2016

$i .$ $P {O}_{4}^{3 -} + H C l \left(a q\right) \rightarrow H P {O}_{4}^{2 -} + C {l}^{-}$
$i i .$ $H P {O}_{4}^{2 -} + H C l \left(a q\right) \rightarrow {H}_{2} P {O}_{4}^{-} + C {l}^{-}$
$i i i .$ ${H}_{2} P {O}_{4}^{-} + H C l \left(a q\right) \rightarrow {H}_{3} P {O}_{4} \left(a q\right) + C {l}^{-}$

#### Explanation:

So how do you do it?

Any chemical reaction CONSERVES mass AND charge. What do I mean? With respect to conservation of mass, If I start with 10 g of reactants (from all sources), AT MOST I can get 10 g products (and in practice I am not even going to get that). To reiterate, mass is conserved in every chemical reaction. A quantity of sodium phosphate represents a specific mass, and is conserved throughout the reaction.

Not only mass is conserved, but CHARGE is conserved. The 3 reactions reflect this. On the LHS (left hand side) of (i) there was a charge of -3; on the RHS, there is also a charge of -3, as required.

Now it may seem that chemical reactions are quite complicated, but if you look at them, they will always be balanced; that is they conserve mass and charge. It is your job to make chemical sense, and to observe conservation.