Hey there!
Mn + HI → H₂ + MnI₃
Balance I.
1 on the left, 3 on the right. Add a coefficient of 3 in front of HI.
Mn + 3HI → H₂ + MnI₃
Balance H.
3 on the left, 2 on the right. Multiply everything else by 2.
2Mn + 6HI → H₂ + 2MnI₃
Now we have 6 on the left and 2 on the right. Add a coefficient of 3 in front fo H₂.
2Mn + 6HI → 3H₂ + 2MnI₃
Balance Mn.
2 on the left, 2 on the right. Already balanced.
Our final balanced equation:
2Mn + 6HI → 3H₂ + 2MnI₃
Hope this helps!
