How do you balance these equations?

Question

#H_3PO_4 (aq) + Mg(OH)_2(aq) -> Mg_3(PO_4)_2(aq) + H_2O(l)#
#C_4H_10(g) + O_2 (g) -> CO_2 (g) + H_2O(g)#

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Answer 1 · 2016-12-03T06:49:44

The same way you balance all equations: conserve mass and charge.

#H_3PO_4(aq) + Mg(OH)_2(aq) rarr MgHPO_4(aq) + 2H_2O(l)#

#C_4H_10(g) + 13/2O_2(g) rarr 4CO_2(g) + 5H_2O(g)#

We have thus stoichiometrically balanced an acid-base, and a combustion reaction. #"Garbage in equals garbage out."#

If you like you can double the combustion reaction to remove the non-stoichiometric coefficient in the combustion reaction:

#2C_4H_10(g) + 13O_2(g) rarr 8CO_2(g) + 10H_2O(g)#

I prefer the former reaction inasmuch as it is easier to specify equivalent masses of hydrocarbon and dioxygen.