Based on the reduction potentials listed in the textbook appendix, which of the following redox reactions do you expect to occur spontaneously?  

w. 2al(s)+3pb2+ (aq) → 2al3+ (aq)+3pb(s)  
x. fe(s)+cr3+ (aq) → fe3+ (aq)+cr(s)  
y. ca2+ (aq)+zn(s) → ca(s)+zn2+(aq)  
z. 2cu+(aq)+co(s) → 2cu(s)+co2+ (s)

a. w only
b. x, y and z
c. y only
d. x and z
e. z only
f. x and y
g. w, x and z
h. x and y
i. w and z

The redox reactions that occur spontaneously are Reaction W and Reaction Z.

Explanation:

For the reaction to be spontaneous, the Gibbs free energy of the reaction must come out to be negative.

Relationship between standard Gibbs free energy and standard electrode potential follows:

For a reaction to be spontaneous, the standard electrode potential must be positive.

To calculate the of the reaction, we use the equation:

      .......(1)

Substance getting oxidized always act as anode and the one getting reduced always act as cathode.

The chemical reaction follows:

We know that:

Calculating the using equation 1, we get:

As, the standard electrode potential is coming out to be positive. So, the reaction is spontaneous.

The chemical reaction follows:

We know that:

Calculating the using equation 1, we get:

As, the standard electrode potential is coming out to be negative. So, the reaction is not spontaneous.

The chemical reaction follows:

We know that:

Calculating the using equation 1, we get:

As, the standard electrode potential is coming out to be negative. So, the reaction is not spontaneous.

The chemical reaction follows:

We know that:

Calculating the using equation 1, we get:

As, the standard electrode potential is coming out to be positive. So, the reaction is spontaneous.

Hence, the redox reactions that occur spontaneously are Reaction W and Reaction Z.

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