1) Which represents the driving force for the boiling of water (i.e. which chang

Question

1) Which represents the driving force for the boiling of water (i.e. which change makes the process occur)?

A Neither the change in H and S

B The change in S only

C Both the change in H and S

D The change in H only

2) In order for a process to be spontaneous, the change in energy of the universe must always be positive. Recall: Suniverse = Ssystem + Ssurroundings Which of the following represent the change of S of the universe when this process OCCURS?

A The decrease in entropy of the system adds to the decrease in entropy of the surroundings

B The increase in entropy of the system adds to the increase in entropy of the surroundings

C The increase in entropy of the system overcomes the decrease in entropy of the surroundings

D The increase in entropy of the surroundings overcomes the decrease in entropy of the system

Explanation / Answer

Q1.

note that boiling water --> increases its enthalpy ( i.e. dH is positive) therefore it can't be

the driving force is that ---> it increases its entropy, that is dS is positive, and this aids in the negative symbol for dG

d G = dH - T*dS

we need dG to be negatve

so just B

Q2.

a) decrease in system, decrease in entopy.... this will be negative

b) dSsystem + dSsurroundings --> this will be always positive

c) dSsystem > dSsurrounginds so dSsystem will make possitive after substraction, this is possitive in universe

d) if increase in entropy and decrease in entropy then

dSsurroundings > dSsystem so

this will be possitive aswell

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