Question

1) Which of the following makes formation of a solution from two pure chemical substances more likely to occur? a) If randomness increases when a solution forms b) If energy decreases when a solution forms c) If energy increases when a solution forms d) Both a and b e) Both a and c 2) What is the value for the van't Hoff factor (1) for Cu(NO3)2? a) i=1 b) i=2 c) i=3 d) i=4 e) i>4 3) For which of the folling pure chemical substances will sº = 0.0 J/molok when T = 25.0 °C? a) O2(g) b) O3(g) c) FeCl3(s) d) Both a and b e) None of the above 4) For a chemical reaction to be spontaneous for standard conditions, which of the following must be true? a) AS rxn < 0 b) AS rx > 0 c) AGºrn0 d) Both a and c e) Both b and c

Answer 1

1, when a solution forms by mixing two pure chemical substances, randomness of the solution increases and the the particles in solution are more distorted. also for the formation of solution, the bond between the molecules should be breaken down to form new bonds between the new molecules, so formation of the new bonds require energy for bond breaking. so when formation of solution, the energy of the solution decreases.

so answer is option d, both a and b.

randomness increase when a solution forms & energy decreases when solution forms.

2.the vont foff factor a ionic substance is the no. of ions that forms when the ion dissociates.

Cu(NO₃)₂ it consist of 2+1= 3 ions.

so von't hoff factor is 3

answer is option c

3. standard entropy of the pure substane, is the entropy of a substance at 1 atm pressure and standard temperature of 273 K.

standard entropy for

oxygen is 205.15

ozone is 238.92

ferric chloride is 344.20

since none is having standard entropy of 0,

answer is none of the above. option d.

4, for a reaction to be spontaneous the gibbs free energy should be negative.

ΔG = ΔH - TΔS

so if delta s is greater than zero,

so the answer is option e, both b and c are correct.

note: please do like the answer.