Consider the following cell: Fe (s) | Fe^2 (aq) | Ag (aq) | Ag (s) What would be

Question

Consider the following cell: Fe (s) | Fe^2 (aq) | Ag (aq) | Ag (s) What would be the best way to make the cell potential more positive? Increase the Fe^2 concentration and decrease the Ag^* concentration Decrease the Fe^2 concentration and increase the Ag^* concentration Increase the Fe^2 concentration and Increase the Ag^* concentration Decrease the Fe^2 concentration and decrease the Ag^* concentration Based upon the E* table, which of the following would be the best (strongest) reducing agent? Sn^2+ Ni^2+ Sn Ni In class, we demonstrated how some metals spontaneously dissolve in hydrochloric acid. Given the E* table on the data page, which of these metals will oxidize and dissolve in 1.0 M HCI? Ni Ag Both Ni and Ag will dissolve in 1.0 M HCI Neither Ni or Ag will dissolve in 1.0 M MCI If takes 44 minutes for a 0.80-g sample of radioactive^44 K to decay to 0.20-g of^44 K. what is the approximate half-life of 4, ^44 K ? 22 minutes 44 minutes 88 minutes 176 minutes What decay product is produced in the following reaction involving the Lanthanides:^135 Nd -^135 Pr + ? alpha particle beta particle neutron particle positron particle

Explanation / Answer

A )

We use Nernst equation.

Ecell = E0cell – (RT/nF) x ln Q

Here Q is the reaction quotient. In this reaction , Q = [Fe2+]/[Ag+]2

When we increase the concentration of iron ion and the decrease the concentration of silver ions, right side will become more positive since ln Q will become more positive.

For example ln Q = 0 when Q =1

Ln Q = -0.65315 when Q = 0.5

More negative value will make more positive value due to the presence of minus sign to the right side and so the Option A explains it correctly.

B.

Chemical species that has more tendency to undergo oxidation will be good reducing agent.

Standard reduction potential :

Ni2+ + 2e- --- > Ni (s)         E0red = -0.23 V

Sn2+ + 2e- --- > Sn(s)          E0red = -0.14 V

Sn2+ will have more tendency to get reduced than Ni since the reduction potential of Sn2+ is less negative.

This shows that metal Ni has more tendency to undergo oxidation and so it will be good reducing agent among all.

Ans : D. Ni.

C.

HCl is dissolved by the metal that has less standard electrode potential than H2 ( E0­red = 0V).

For Ag   E0­red = 0.80 V

For Ni E0­red = -0.25 V

In order to dissolve the HCl, metals should replace H+ from the HCl and that is done by the metal which has less reduction potential than H2.

So the answer is A. Ni.

D

Half life is the time that is taken by the substance to decrease its amount by half.

Here initial amount of radioactive substance is 0.80 g and when it reduces to 0.20, it took 44 minutes.

Half amount of 0.80 is 0.40 and 0.20 is the half of 0.40.

Time required to to from 0.80 to 0.40 will be (44/2) = 22

And time required from 0.40 to 0.20 will be 44/2 = 22

So the answer is 22 minute.

E

In this example mass number remains same and there is change in atomic number ( decreased by one). This suggests that there is conversion of one proton to neutron.

And in this process positron particle is removed.

Answer : D. Positron particle.

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