Question

how do you balance a redox equation like:
Bi(NO3)3 + Al + NaOH = Bi + NH3 + NaAlO2 ??

Answer 1

Bi(NO3)3 + Al + NaOH = Bi + NH3 + NaAlO2

If you want to balance an equation by inspection, then a good tip is to leave atoms alone and work with the molecules first.

An alternative method depends on how good your basic algebra is?

Bi(NO3)3 + Al + NaOH = Bi + NH3 + NaAlO2

lets say the missing numbers are as below

aBi(NO3)3 + bAl + cNaOH = Bi + dNH3 + eNaAlO2

(I have assumed that the number in front of Bi=1)

by balancing the atoms we can come up with a series of simultaneous equations

Bi a=1
N 3a=d
O 9a+c=2e
Al b=e
Na c=e

so we have five equations and five unknowns which we can solve.

a=1 so d=3 which is easy!

substitute value for a into the third equation

9+c=2e and we know c=e from the fifth equation
9+e=2e

hence e=9, c=9, and b=9

replace the symbols for numbers in the original

Bi(NO3)3 + 9Al + 9NaOH = Bi + 3NH3 + 9NaAlO2

and this method works EVERY time!!