6) Which of the following processes are spontaneous? 1 dissolving more solute in

Question

6) Which of the following processes are spontaneous? 1 dissolving more solute in a saturated solution 111 dissolving more solute in a supersaturated I dissolving more solute in an unsaturated solution oltion A) none of these B C) I and I or which of the following will the entropy of the system increase? D) I, 11, and 111 A) condensation of steam B) reaction of magnesium with oxygen to form magnesium oxide C) reaction of nitrogen and hydrogen to form ammonia D) sublimation of dry ice 8) What is the reduction half-reaction for the following overall cell reaction? Ni2+(aq) + 2 Ag(s) Ni(s) + 2 Ag" (aq) A) Ag(s)+Ag (aq) B) Ag+(aq) + e- Ag(s) C) Ni2+(aq) + 2 e. Ni(s) D) Ni2+(aq) + e- Ni(s) 9) A galvanic cell employs the reaction Mg2 +(aq) + Cu(s) Mg(s) + Cu2+(aq) and NaNO3 is the salt used in the salt bridge. During the course of the reaction A) Na+ leaves the salt bridge and enters the anode compartment. B) NaNO3 leaves the salt bridge and enters the anode compartment. C) Nat leaves the salt bridge and enters the cathode compartment. D) NaNO3 leaves the salt bridge and enters the cathode compartment. 10) What is the relation between Go and Eo for the cell reaction below? Ni2+ (aq) + Cd(s)-Cd2+ (aq) + Ni(s) 11) Predict the sign of AS of the system for both of the following. I. 11. 2 C(graphite) + O2(g) 2 CO(g) C4H10(g) C4H10(/) A) AS should be negative for I and negative for II. B) AS should be negative for I and positive for II. C) AS should be positive for I and negative for II. D) AS should be positive for I and positive for II. The volume of 2.0 moles of O2(g) increases from 44 L to 52 L. The pressure of 2.0 moles of 02(8) increases from 1.0 atm to 1.2 atm. 12) Predict the sign of AS for each of the following processes, which occur at constant te I. II. A) I: AS negative; II: AS negative B) I: AS= negative: 11: AS: positive C) l: AS-positive; II: AS= negative D) I: AS- positive; II: AS- positive

Explanation / Answer

6. Dissolving more solute in unsaturated solution is spontaneous.

Because in the unsaturated solution can still dissolve solute upto saturation point hence any external aid is not required. While in other cases (saturated and supersaturated) amount of solute in solution is maximum (saturated) and more than the required amount ( supersaturated). Hence further dissolution of solute cannot occur spontaneously.

7. Sublimation of dry ice.

Sublimation is a process of conversion of solid to gas directly without passing through liquid state.

The entropy ( randomness) is high in gases followed by liquid and gases.

Hence sublimation reaction increase the entropy of the system in which it is taking place. So sublimation of dry ice(solid CO2) to gaseous CO2 increases the entropy of the system

8. In the above reaction Ni is undergoing reduction hence the reduction half reaction is

Ni2+ (aq) + 2 e- -------------> Ni(s)

9. Na+ leaves the salt bridge and enters the cathodic compartment

because in cathodi compartment the Cu2+ ions in the electrolyte undergoes reduction to get deposited as solid Cu on the electrode leaving back the (SO4)2- ion(electrolyte is CuSO4) hence to balance the electrical neutrality Na+ ions(oppositely charged ions to( SO4)2- ions) enters the cathodic compartment.

10. Ni2+(aq) + 2e- ------> Ni(s)

   Cd(s) ----------> Cd2+(aq) + 2e-

hence the number oF electron trasfer =2 i,e n=2

therefore the equation for channge in free energy and std. Electrode potential is

delta G = -nFE0

   =-2FE0

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