Question

BALANCE THE EQUATION
P₂I₄+H₂O → H₃PO₄+PH₄I

Answer 1

let the balancing coefficients be a,b,c,d. a before p2i4, b before h2o, and so on.
next, balance for all the atoms,
like to ensure the no. of P atoms on lhs and rhs of the equation,
2a=c+d
for I atoms,
4a=d
for H atoms,
2b=3c+4d
for O atoms,
b=4c
next, find relations between all the coefficients, let them be all in the form of a, say.
solving those equations, we have,
 c=8a/9
b=32a/9
d=10a/9
a will get cancelled on all sides.
convert the coefficients into natural numbers.
9P2I4+32H2O=8H3PO4+10PH4I
the equation is balanced now.
ask if you still have doubts..