Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level Chemistry > Energetics I > Flashcards

Energetics I Flashcards

1
Q

What is the enthalpy change in a reaction?

A

The heat change in a reaction at a constant pressure.

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

What are the units for enthalpy change?

A

Kj mol^-1

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

What is an example of an endothermic reaction?

A

A thermal decomposition reaction

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

In an endothermic reaction, do the products have higher energy than the reactants?

A

Yes

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

In an exothermic reaction do the products have lower energy than the reactants?

A

Yes

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

What is an example of an exothermic reaction?

A

A combustion reaction

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

To break a bond what needs to happen?

A

Energy needs to be absorbed

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

In an endothermic reaction, are bonds broken in the reactants?

A

Yes

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

In an exothermic reaction, when bonds are formed, is energy released?

A

Yes

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

What is the bond enthalpy?

A

The amount of energy required to break 1 mole of a bond type in a molecule in its gaseous state.

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

Enthalpy change =

A

Total energy to break bonds- total energy released when bonds are formed

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

When products are being produced in an exothermic reaction, are bonds made?

A

Yes

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

What is calorimetry used to work out?

A

Thr enthalpy change of combustion

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

Describe the steps involved in calorimetery

A

1) A fuel is burned to raise the temperature of the water by a specific amount. The fuel is weighed before and after to work out the mass of the fuel burned.

2) The energy from the fuel is transferred into the water, although some is lost to the surroundings too.

3) A lid is placed on top to prevent heat loss and wind shields. It is placed by the flame to prevent a draught moving the flame.

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

What equation can energy transferred be calculated using?

A

q = mc change in t

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

What is q?

A

The heat energy gained or lost

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is m?

A

The mass of water/the solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is t?

A

Temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the units for heat energy transfer?

A

Joules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the units for mass?

A

Grams

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is c?

A

The specific heat capacity of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is temperature measured in?

A

Kelvin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the specific heat capacity of water?

A

4.18 j/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Enthalpy =..

A

Enthalpy = energy / moles

25
Q

How can the energy from a calorimetry experiment of solutions be calculated?

A

1) Add an acid to a polystyrene cup and measure the temperature.

2) Then, add alkali/solid, stir it, then measure the enthalpy change.

26
Q

State Hess’ law

A

The total enthalpy change of a reaction is independent of the route taken

27
Q

When you’re given formation data, do the arrows point up or down?

A

The arrows point up

28
Q

If you’re given combustion data do the arrows point up or down?

A

Down

29
Q

What are standard conditions?

A

100kPa (1atm) pressure

298k

Standard states

30
Q

Does the temperature go up or down in exothermic reactions?

A

Up

31
Q

Does the temperature go up or down in endothermic reactions?

A

Down

32
Q

The less enthalpy a substance has…

A

The more stable it is

33
Q

What is the activation energy, Ea?

A

The minimum amount of energy required to break the reactant bonds and start a chemical reaction.

34
Q

Can you directly measure the actual enthalpy of a system?

A

No

35
Q

How do you work out enthalpy changes?

A
  • By experiment.
  • Using data books
36
Q

What is the standard enthalpy change of reaction?

A

The enthalpy change when the reaction occurs in the molar quantities shown in the chemical equation, under standard conditions

37
Q

What is the standard enthalpy change of formation?

A

The enthalpy change when one mole of a compound is formed from its elements in their standard states, under standard conditions.

38
Q

What is the standard enthalpy change of combustion?

A

The enthalpy change when 1 mole of a substance is completely burned in oxygen, under standard conditions.

39
Q

What is the standard enthalpy change if neutralisation ?

A

The enthalpy change when an acid and an alkali react together, under standard conditions, to form 1 mole of water

40
Q

What is the mean bond enthalpy?

A

The energy needed to break one mole of bonds in in the gas phase, averaged over many different compounds.

41
Q

Why might the value obtained from carrying out enthalpy experiments be different from the data book value for enthalpy change?

A
  • Conditions may not have been in standard states.
  • Incomplete combustion may have occurred.
  • Heat energy may have been lost to the surroundings.
  • There may have been a wrong approximation of the Specific Heat capacity of the solution.

-

42
Q
A
43
Q

What is the standard lattice enthalpy?

A

The energy change when 1 mole of an ionic solid is formed from its gaseous ions under standard conditions

44
Q

What is the standard lattice energy a measure of?

A

Ionic bond strength

45
Q

The more negative thr lattice energy…

A

The stronger the ionic bonding

46
Q

What needs to be assumed when working out the theoretical lattice energy?

A
  • That all ions are spherical
  • That the charge is evenly distributed
47
Q

Is it true that the polarisation of ionic bonds leads to some covalent character in ionic lattices?

A

Yes

48
Q

What is thr polarising power affected by?

A
  • Ionic charge
  • Ionic radius
49
Q

Is it true that bonds are polar if the difference in Pauling electronegativity is greater than 0.4?

A

Yes

50
Q

Is bond breaking endothermic or exothermic?

A

Endothermic

51
Q

Is bond making endothermic or exothermic?

A

Exothermic

52
Q

What is the enthalpy change of hydration?

A

Thr enthalpy change when 1 mole of gaseous ions dissolves in water.

53
Q

What is the enthalpy change of solution?

A

The enthalpy change when 1 mole of solute dissolves in water

54
Q

What are the steps in working out the enthalpy change of solution?

A

1) Ionic lattice and dissolved ions go on the top.

2) Connect ionic lattice to the gaseous ions by the lattice energy

3) Connect the gaseous ions to the dissolved ions by the hydration enthalpies of each ion.

55
Q

What is the enthalpy change of hydration affected by?

A

Ionic charge and ionic radius

56
Q

What is entropy?

A

The measure of the disorder of a system

57
Q

The nore disordered a system is, the higher the what?

A

The higher the entropy

58
Q

Continue from energetics 2 page and entropy page

A
59
Q
A

A-level Chemistry (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions