[HelloMotto]

in an equation, how do i know if an ion is an spectator ion or not?

for example, in equation

Ag + CN^- + O2 + H2O ----> Ag(CN)2^-1 + OH^-

i didnt know cynaide ion was a spectator ion, thus CN isnt oxidzed or reduced. So in situations like this, how do i know if a specific ion is a spectator or not?

[Borek]

CN^- here is not a spectator - it reacts, even if it is neither reduced nor oxidized.

To check what is reduced and oxidized, you can calculate oxidation numbers for each element in each compound - whichever changes between left and right side of reaction equation, was either reduced or oxidized.

[HelloMotto]

ok i have another question regarding this topic.
HNO3 + I2 ---> HIO3 + NO2 + H2O

im trying to balance this equation using the oxidation number method, but i keep getting the wrong answer. I suspect i didnt figure out the right oxidation numbers for each element.

the oxidastion numbers i got were

HNO3 + I2 ---> HIO3 + NO2 + H2O
+1/+5/-2(3), 0 ---> +1/+5 /-2(3), +1(2)/-2

is this right?

[Borek]

Check N in NO₂.

[HelloMotto]

oh i missed that.

fgor NO2, it would be +4/-2(2).

so nitrogen gains 1 electron X 5 = 5 electrons
Iodine loses 5 electrons x 1 = 5 electrons.

so i multiply the compound with nitrogen by the coefficient 5 and multiply the compound with Iodine by 1.

and i get

5HNO3 + I2 ---> HIO3 + 5NO2 + H2O.

now obviously this isnt balanced. I've used thsi method for other questions and it worked. But its not working for this equation and its really frustrating :-(. What did i do wrong?

[Borek]

Iodine loses 5 electrons, but you have I₂, not I.

Besides, multiplying will help you find the correct ratio between I₂ and HNO₃, you have to balance other atoms/molecules by hand.