What is the balanced chemical equation of Li(s) + H3PO4(aq) ?

Question

Naomi Aronson · Accepted Answer

#6"Li"_text((s]) + 2"H"_3"PO"_text(4(aq]) -> 2"Li"_3"PO"_text(4(aq]) + 3"H"_text(2(g]) uarr#

Lithium metal will react with phosphoric acid to produce lithium phosphate, #"Li"_3"PO"_4#, and hydrogen gas, #"H"_2#.

#"Li"_text((s]) + "H"_3"PO"_text(4(aq]) -> "Li"_3"PO"_text(4(aq]) + "H"_text(2(g]) uarr#

Observe that only the atoms of lithium and hydrogen are out of balance in this chemical equation.

More specifically, you have one lithium atom on the reactants' side, and three on the products' side. This means that you need to multiply the former by #3#

#3"Li"_text((s]) + "H"_3"PO"_text(4(aq]) -> "Li"_3"PO"_text(4(aq]) + "H"_text(2(g]) uarr#

The hydrogen atoms are the only ones that are still out of balance; there are three of them on the side of the reactants and only two on the side of the products this time.

This implies that you're going to have to multiply the hydrogen atoms on the reactants' side by #2# and those on the products' side by #3# to get a total of six atoms on each side.

#3"Li"_text((s]) + 2"H"_3"PO"_text(4(aq]) -> "Li"_3"PO"_text(4(aq]) + 3"H"_text(2(g]) uarr#

Now you've unbalanced the number of phosphorus and oxygen atoms. To fix this, you can treat the phosphate anion, #"PO"_4^(3-)#, as a unit.

This means that you will need to multiply the lithium phosphate by #2# to get

#3"Li"_text((s]) + 2"H"_3"PO"_text(4(aq]) -> 2"Li"_3"PO"_text(4(aq]) + 3"H"_text(2(g]) uarr#

Finally, balance the lithium atoms again by multiplying the lithium metal by #6# instead of by #3#.

#6"Li"_text((s]) + 2"H"_3"PO"_text(4(aq]) -> 2"Li"_3"PO"_text(4(aq]) + 3"H"_text(2(g]) uarr#

The chemical equation is now balanced as a result.

Noah Aldrich · Answer

undefined The balanced chemical equation for the reaction between solid lithium (Li) and aqueous phosphoric acid (H3PO4) is:

2Li(s) + 2H3PO4(aq) → 2LiH2PO4(aq) + H2(g)