Respuesta :

N goes from +5 to +2, a gain of 3 electrons
Each I goes from -1 to 0, a loss of 1 electron
Need a 3:1 ratio of HI to HNO3
Since I is I2 on the product side, use a 6:2 ratio
2HNO3 + 3HI= 2NO + 3I2 + 4H2O