Module 3 Chapter 9 Flashcards

1
Q

What is enthalpy defined as

A

The total heat content within a system

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

What is a chemical system

A

All the atoms, ions, and molecules that make up all the chemicals in a region of observable space

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

What is enthalpy measured by

A

The heat absorbed from or released into the surroundings.

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

what does the universe consist of

A

The systems and surroundings

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

What is the law of conservation of energy

A

Energy is not created or destroyed. It is only transferred during the process.

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

What is the heat energy released by a chemical reaction equal to

A

It is equal to the heat energy gained by the surroundings.

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

What is the formula for enthalpy change

A

^H = H (products) - H (reactants)

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

Because of the conservation of energy what happens to the energy

A

The change in energy has to be transferred and this transfer takes place between the system and the surroundings.

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

What are examples of exothermic reactions

A

Combustion
neutralisation
Oxidation reactions
Displacement

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

What is an exothermic reaction

A

A reaction that transfers energy to their surroundings and can be identified by an increase in the temperature of the surroundings.

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

What is the energy transfer in an exothermic reaction

A

Energy transfer from systems to surroundings

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

What are the enthalpies of the products and reactants relative to each other in an exothermic reaction and what is ^H

A

H products < H reactants
^H is negative

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

What is activation energy

A

The minimum amount of energy required for a reaction to take place

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

What does the enthalpy profile diagram and reaction profile diagram of an exothermic reaction look like

A

DRAW IT

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

What can an exothermic reaction be identified by

A

An increase in the temperature of the surroundings

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

What is an endothermic reaction in terms of energy and temperature

A

A reaction that takes in energy from its surroundings and can be identified by a decrease in the temperature of the surroundings.

17
Q

What is the relative energy of the products and reactants in an endothermic reaction and what is ^H

A

H products > H reactants
^H is positive

18
Q

What does the enthalpy profile diagram and reaction profile diagram look like for an endothermic change

A

DRAW IT

19
Q

If the reaction conditions change what happens

A

The reactants and products enthalpy can change which means ^H can change as well.

20
Q

What are standard conditions

A

Standard pressure - 100kPA
Standard temperature - 298K (25 C)
Standard concentration - 1mol/dm3 (only with solutions)
Standard state - the physical state of a substance under standard conditions

21
Q

What is the symbol for when an experiment is done at standard conditions

A

DRAW IT

22
Q

What is 1 atmosphere in kPA

A

101 kPA =101,000 Pa = 1 atm

23
Q

What is enthalpy change of formation

A

The enthalpy change when 1 mole of a compound is formed from its elements under standard conditions with all reactants and products in their standard state.

24
Q

What is the enthalpy change of formation of an element always

A

0 KJ/mol

25
Q

What is the enthalpy change of combustion

A

When 1 mol of a substance reacts with oxygen under standard conditions with all reactants and products in their standard state.

26
Q

What is enthalpy change of neutralisation

A

The enthalpy change that accompanies a reaction of an acid and base to form 1 mole of water under standard conditions with all reactants and products in their standard state.

27
Q

What is the enthalpy change for neutralisation always

A
  • 57 Kj/mol
28
Q

What is the equation to find the heat energy in a temperature change

A

^q = m x c x t
Heat energy (j) = mass (g) x specific heat capacity (J/gk) x temperature change (K)

29
Q

What can you use to dirt mine the enthalpy change of combustion

A

A calorimeter

30
Q

What does a calorimeter experiment look like

A

DRAW IT

31
Q

How can you use a calorimeter to work out the enthalpy change of combustion

A

Record the volume of water
Record the mass of the fuel before and after heating
Record the temperature change in water
Use q = m x c x ^t
Find the moles of fuel burnt

32
Q

Why will the calculated change be less than the actual value

A

. Non standard conditions
. Droughts affect the flame
. Heat transferred to beaker. Surroundings instead of H2O/ Heat loss
. Soot formed on beaker - incomplete combustion
. Evaporation of fuel - weigh as soon as possible after extinguishing flame

33
Q

What are average bond enthalpies used for

A

For bonds that occur in different molecules

34
Q

What does the bond enthalpy depend on

A

The value depends on the bond environment

35
Q

What are the limitations of average bond enthalpy

A

Using average bond enthalpies rather than the actual energy involved
The energy of individual bonds would be slightly different due to the different environments

36
Q

What is Hess’ law

A

The enthalpy change of a reaction is independent of the route taken if initial and final conditions are the same.

37
Q

What is the definition of average bond enthalpy

A

The average energy required to break one mole of a specified type of bond in gaseous molecules, averaged over a range of compounds

38
Q

Enthalpy change of a reaction definition

A

Enthalpy change that accompanies a reaction in the molar quantities stated in the equation under standard conditions with all reactants and products in standard state.