How would you balance PCl5 + H2O -->H3PO4 + HCl?

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Answer 1 · 2015-10-25T13:30:57

$PCl_5$ + $4H_2O$ = $H_3PO_4$ + $5HCl$

Just create a tally sheet for all the elements involve.

$PCl_5$ + $H_2O$ = $H_3PO_4$ + $HCl$

Left side:
P = 1
Cl = 5
H = 2
O = 1

Right side:
P = 1
Cl = 1
H = 3 + 1 (DO NOT ADD IT UP YET)
O = 4

Start balancing the easiest element, in this case, the Cl.

Left side:
P = 1
Cl = 5
H = 2
O = 1

since $HCl$ is a substance, you need to also multiply its H by 5.

Right side:
P = 1
Cl = 1 x 5 = 5
H = 3 + (1 x 5) = 8
O = 4

$PCl_5$ + $H_2O$ = $H_3PO_4$ + $5HCl$

Now the H atom on the left side is not balance with the right side, we have to multiply the H on the left side by 4.

Left side:
P = 1
Cl = 5
H = 2 x 4 = 8
O = 1 x 4 = 4

Again, since $H_2O$ is a substance, you also need to multiply its O by 4.

Right side:
P = 1
Cl = 1 x 5 = 5
H = 3 + (1 x 5) = 8
O = 4

$PCl_5$ + $4H_2O$ = $H_3PO_4$ + $5HCl$

The equation is now balanced.