Question

How would you balance the following double replacement equation: Al(NO3)3 + Na3PO4 = AlPO4 + NaNO3?

Answer 1

`Al(NO_3)_3(aq) + Na_3PO_4(aq) rarr Al(PO_4)(s)darr + 3NaNO_3(aq)`

Explanation:

All nitrates are soluble; all salts of the alkali metals are soluble; all phosphates are insoluble. This is as far as I know; I will just look up at the solubility of aluminum phosphate. Wiki tells me it has a `K_(sp) = 6.3 xx 10^(-19)`; so rules of thumb are entirely appropriate here.