chemistry - unit 2.2 Flashcards

1
Q

What is the standard enthalpy of formation?

A

The enthalpy change when one mole of a substance is formed from its elements in their standard states.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the standard state of a substance?

A

Its most stable state at a pressure of 1 atmosphere and at a specified temperature, usually taken as 298 K.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How can the standard enthalpy of a reaction be calculated?

A

From the standard enthalpies of formation of the reactants and products.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the entropy (S) of a system?

A

A measure of the degree of disorder of the system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The greater the degree of disorder…

A

…the greater the entropy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What have low disorder and what have high disorder?

A

Solids have low disorder and gases have high disorder.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When does entropy increase?

A

When temperature increases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When is there a rapid increase in the entropy of a substance?

A

At its melting point and even a more rapid and larger change in entropy at the boiling point.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does the second law of thermodynamics state?

A

The total entropy of a reaction system and its surroundings always increases for a spontaneous process.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What increases the entropy of the surroundings?

A

Heat energy released by the reaction system into the surroundings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What decreases the entropy of the surroundings?

A

Heat energy absorbed by the reaction system from the surroundings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the third law of thermodynamics state?

A

The entropy of a perfect crystal at 0K is zero.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the standard entropy of a substance?

A

The entropy value for the substance in its standard state.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

If the change in free energy between reactants and products is negative, what may happen?

A

A reaction may occur and the reaction is said to be feasible.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a feasible reaction?

A

One that tends towards the products rather than the reactants. This does not give any indication of the rate of reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can the feasibility of a chemical reaction under standard conditions be predicted from?

A

The calculated value of the change in standard free energy.

17
Q

How can the temperatures at which a reaction may be feasible be estimated?

A

By considering the range of values of T for which:
DeltaG < 0.

18
Q

Under non-standard conditions, when is any reaction feasible?

A

If DeltaG is negative.

19
Q

At equilibrium, what is DeltaG?

A

0

20
Q

How long will a reversible reaction proceed spontaneously?

A

Until the composition is reached where DeltaG = 0.

21
Q
A