Question

Which number should be placed in the blank to make the equation balanced? ___ Mg + P4 → 2 Mg3P2

Answer 1

\[Mg+P_4->2Mg_3P_2\]Look at each of the products and reactants...first I see:
\[2Mg_3\]That requires 6 Mg atoms...so if you put a 6 in front of the left Mg the Mgs balance.

Next:\[2P_2\]That requires 4 P atoms...which you already have on the left...so the equation is otherwise balanced (after you make the correct to the Mg atoms).

Answer 2

The balanced equation is as follows:

6Mg + P4 --> 2Mg3P2