Find the n-factor of H3PO4 in the given reaction:
<img alt="\mathrm{H}_{3} \mathrm{PO}_{4}+\mathrm{Ca}(\mathrm{OH})_{2} \rightarrow \mathrm{CaHPO}_{4}+2 \mathrm
In the case of acids, the n-factor is the basicity or the number of replaceable hydrogen atoms from the acid. In the case of H3PO4, the number of replaceable hydrogen atoms is 2.