Question

Can anyone solve this chemistry question please?

Answer 1

Well, nitrate ion is the oxidizing agent....

Explanation:

...the which I presume is reduced to `NO_2`..

`stackrel(+V)NO_3^(-)+2H^(+) +e^(-)rarr stackrel(+IV)NO_2(g) + H_2O(l)`

And nickel should be oxidized to `Ni^(2+)`:

`Ni(s) rarr Ni^(2+) + 2e^(-)`

And so we adds TWO of the former to ONE of the latter....

`Ni(s) + 2NO_3^(-)+4H^(+) +2e^(-)rarr Ni^(2+) +2NO_2(g) + 2H_2O(l)+ 2e^(-)`

..to give after cancellation....

`Ni(s) + 2NO_3^(-)+4H^(+) rarr Ni^(2+) +2NO_2(g) + 2H_2O(l)`

And now we work out `E_"cell"`...the which is a bit difficult in that we ain't got a Table of standard redox potentials in front of us...as it was in front of you when they set the problem...

From this site, we learn that....

`Ni^(2+) + 2e^(-) rarr Ni(s)` `;E^@=-0.25*V`...and...

`NO_3^(-)+2H^(+) +e^(-)rarr NO_2(g) + H_2O(l)` `;E^@=+0.80*V`

And so.....

`Ni(s) +2HNO_3+2H^(+) rarr Ni^(2+) +2NO_2(g) + 2H_2O(l)`

And `E_"cell"^@={0.80-(-0.25)}*V=+1.05*V`

And since the potential difference is POSITIVE....the equation as written is spontaneous.

As regards the second question, the reaction of aluminum with carbonate ion....you will have to give us a little more context, I am not seeing the premise of the question.