Question

1.The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ______ V.

Sn²⁺(aq) + 2 Fe³⁺(aq) → 2 Fe²⁺(aq) + Sn⁴⁺(aq)

A.+0.62 B.+0.46 C.-0.46 D.+1.39 E.+1.21

2.Consider an electrochemical cell based on the reaction:

2 H⁺(aq) + Sn(s) → Sn²⁺(aq) + H₂(g)

Which of the following actions would change the measured cell potential?

A.increasing the pressure of hydrogen gas in the cathode compartment

B.increasing the pH in the cathode compartment

C.Any of these options will change the measured cell potential.

D.lowering the pH in the cathode compartment

E.increasing the [Sn²⁺] in the anode compartment

3.Which equation correctly represents the first ionisation of phosphorus?

4.On a phase diagram, the critical pressure is ______.

A.the pressure below which a substance is a solid at all temperatures

B.the pressure required to liquefy a gas at its critical temperature

C.the pressure required to melt a solid

D.the pressure above which a substance is a liquid at all temperatures

E.the pressure at which a liquid changes to a gas

Answer 1

Sn2+Sn4+ + 2e at anode Eo red=0.15V

Fe3+ +eFe2+   Eo red=0.77

1) Eocell=Eo red,cathode-Eo red,anode=0.77-0.15=0.62V

2) C.Any of these options will change the measured cell potential

reason- there exists an equilibrium between the reduction half cell reaction at cathode and oxidation half cell reaction at anode . Ecell is measured by nerst equation as follows-

Ecell=Eo cell-RT/nF ln Q

Q=reaction quotient=[C]^c [D}^d/[A]^a [B]^b

for     aA+bBcC+dD

so if we change the concentration of either ions in the cathode or anode concentration ,its Ecell changes.

Here any change in H+ or Sn2+ concentration due to change in pH or pressure or other changes Ecell

3)P(g)P+(g) + e

beccause ionization means removal or addition of electrons in gaseous state

4)B.the pressure required to liquefy a gas at its critical temperature

it is the pressure at critical point(refer phase diagrams)