Predict whether the following reactions are spontaneous. 1. Pd(aq)2+H2g>Pd(s)+2H(aq+) Pd(aq2+) +2e- > Pd(s)
E° 0.987 v
2. Sn(aq4+)+H2(g)>Sn(aq2+)+2H+ Sn(aq4+)+2e>Sn(aq)2+
E°0.154V
3. Ni(aq2+)+H2(g)>Ni(s)+2H(aq+) Ni(aq2+) +2e>Ni(s)
E° -0.250 V
4. Cd(aq2+)+H2(g> Cds)+2H(aq)+ Cd(aq)2 + +2e >
Cd(s) E°-0.403 v
From your answers, decide which of the above metals could be reduced by hydrogen

1. spontaneous

2. spontaneous

3. Not Spontaneous

4. Not Spontaneous

Palladium and Sn^4+ can be reduced by hydrogen.

Explanation:

If we look at the electrochemical systems represented above, we will notice that in the first two cells, the metal should be reduced looking at the positive electrode potential of the process. This means that hydrogen can reduce the both metals. Electrons flow from the H2(g)/H^+(aq) half cell to the metal/metal ion half cell.

Similarly, when the standard electrode potential is negative, electrons flow from the metal/metal ion electrode to the hydrogen electrode.

Based on the reaction equations, a process is spontaneous if it gives a positive E°cell hence the answers above.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

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