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IB Chemistry > Reactivity 1.2 > Flashcards

Reactivity 1.2 Flashcards

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1
Q

What sort of process is bond breaking?

A

Endothermic

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2
Q

What sort of process is bond forming?

A

Exothermic

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3
Q

In terms of bond breaking and forming, describe when a reaction would be exothermic.

A

The energy released from forming new bonds is greater than the energy needed to break existing bonds

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4
Q

In terms of bond breaking and forming, describe when a reaction would be endothermic.

A

The energy needed to break existing bonds is greater than the energy released from forming new bonds

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5
Q

To use average bond enthalpies to determine an enthalpy change of reaction, which state must all reactants and products be

A

Gas

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6
Q

Describe how to calculate the enthalpy of reaction using bond enthalpy values

A

The sum of the energies needed to break bonds in the reactants minus the energy released when the new bond are formed in the products

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7
Q

Define bond enthalpy

A

The enthalpy change needed to break one mole of bonds in a gaseous molecule averaged over similar compounds

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8
Q

Explain why experimentally determined enthalpy of reaction values are always different from theoretical enthalpy of reaction values calculated using bond enthalpy data

A

Bond enthalpy values in the data booklet are averages of that bond in many different molecules, whilst the experimental data will be determined using a specific molecules.

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9
Q

Explain why the bond enthalpy values in the data booklet are averages

A

They are an average value of the bond enthalpy for the same bond in different environments or molecules

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10
Q

Determine the enthalpy required to break all the bonds in 1.00 mol of nitrogen molecules

A

(+) 945 kJ mol⁻

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11
Q

Determine the enthalpy released when forming all the bonds in 1.00 mol of nitrogen molecules

A

(-) 945 kJ mol⁻

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12
Q

Determine the enthalpy required to break all the bonds in 1.00 mol of oxygen molecules

A

(+) 498 kJ mol⁻

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13
Q

Determine the enthalpy released when forming all the bonds in 1.00 mol of oxygen molecules

A

(-) 498 kJ mol⁻

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14
Q

Determine the enthalpy required to break all the bonds in 1.00 mol of carbon dioxide molecules

A

(+) 1608 kJ mol⁻

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15
Q

Determine the enthalpy released when forming all the bonds in 1.00 mol of carbon dioxide molecules

A

(-) 1608 kJ mol⁻

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16
Q

Determine the enthalpy required to break all the bonds in 1.00 mol of methane molecules

A

(+) 1656 kJ mol⁻

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17
Q

Determine the enthalpy released when forming all the bonds in 1.00 mol of methane molecules

A

(-) 1656 kJ mol⁻

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18
Q

Determine the enthalpy required to break all the bonds in 1.00 mol of propene molecules

A

(+) 3444 kJ mol⁻

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19
Q

Determine the enthalpy released when forming all the bonds in 1.00 mol of propene molecules

A

(-) 3444 kJ mol⁻

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20
Q

Using section 12 of the data booklet, determine the total enthalpy required to break all the bonds in the following reactants

A

(+) 1898 kJ mol⁻

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21
Q

Using section 12 of the data booklet, determine the total enthalpy required to break all the bonds in the following reactants

A

(+) 2582 kJ mol⁻

22
Q

Using section 12 of the data booklet, determine the total enthalpy required to break all the bonds in the following reactants

A

(+) 6494 kJ mol⁻

23
Q

Using section 12 of the data booklet, determine the total enthalpy released to form all of the bonds in the following products

A

(-) 1997 kJ mol⁻

24
Q

Using section 12 of the data booklet, determine the total enthalpy released to form all of the bonds in the following products

A

(-) 2385 kJ mol⁻

25
Q

Using section 12 of the data booklet, determine the total enthalpy released to form all of the bonds in the following products

A

(-) 8528 kJ mol⁻

26
Q

Using section 12 of the data booklet, calculate the overall enthalpy change of the following chemical reaction

A
  • 99 kJ mol⁻ - MUST INCLUDE THE NEGATIVE SIGN
27
Q

Using section 12 of the data booklet, calculate the overall enthalpy change of the following chemical reaction

A

(+) 197 kJ mol⁻ - MUST INCLUDE THE POSITIVE SIGN

28
Q

Using section 12 of the data booklet, calculate the overall enthalpy change of the following chemical reaction

A
  • 2034 kJ mol⁻ - MUST INCLUDE THE NEGATIVE SIGN
29
Q

A forward reaction has an enthalpy change of +244 kJ mol⁻, what is the enthalpy change for the reverse reaction?

A

-244 kJ mol⁻ - MUST INCLUDE THE NEGATIVE SIGN

30
Q

What is the first thing you should do when calculating the total bond enthalpy for a molecule

A

Draw out the molecule including all of the bonds

31
Q

If a substance in a chemical reaction has a coefficient greater than 1, how would you calculate the total bond enthalpy for the substance

A

Total bond enthalpy for one molecule of the substance multiplied by the coefficient

32
Q

When counting the bonds in a molecule, how can you ensure you do not forget to count a bond

A

Tick off each bond on the molecule drawing once it has been counted

33
Q

Describe the relationship between bond enthalpy and bond length

A

The shorter the bond length, the higher the bond enthalpy

34
Q

Describe the relationship between bond enthalpy and bond polarity

A

The higher the bond polarity, the higher the bond enthalpy

35
Q

Define Hess’s Law

A

The overall enthalpy change for a chemical reaction is the same independent of the route taken as long as the initial and final conditions are the same.

36
Q

Construct an equation to use Hess’s law to determine ΔH

A

ΔH = ΔH1 + ΔH2 + ΔH3

37
Q

Construct an equation to use Hess’s law to determine ΔH1

A

ΔH1 = AH - ΔH3 - ΔH2

38
Q

Construct an equation to use Hess’s law to determine ΔH2

A

ΔH2 = -ΔH1 + ΔH - ΔH3

39
Q

Construct an equation to use Hess’s law to determine ΔH3

A

ΔH3 = -ΔH2 -ΔH1 + ΔH

40
Q

Construct an equation to use Hess’s law to determine ΔH2

A

ΔH2 = ΔH1 - ΔH3

41
Q

Construct an equation to use Hess’s law to determine ΔH5

A

ΔH5 = -ΔH4 + ΔH1 - ΔH6

42
Q

When using Hess’s law describe what you must do to the enthalpy change if you are moving in the opposite direction to the reaction arrow

A

Change the sign OR Change from + to - and vice versa

43
Q

Define the standard enthalpy of formation

A

The enthalpy change when 1 mole of a substance is formed from its constituent elements in the standard states under standard conditions

44
Q

State the standard enthalpy of formation for any element

A

0

45
Q

State the standard enthalpy of formation for hydrogen gas

A

0

46
Q

Describe how to use standard enthalpy of formation data to calculate the standard enthalpy of reaction

A

The sum of the standard enthalpies of formation of the products minus the sum of the standard enthalpies of formation of the reactants.

47
Q

Construct a balanced symbol equation to represent the standard enthalpy of formation of 1.00 of water

A

H₂ (g) + 1/2O₂ (g) –> H₂O (l)

48
Q

Construct a balanced symbol equation to represent the standard enthalpy of formation of 1.00 of benzene

A

3H₂ (g) + 6C (s) –> C₆H₆ (l)

49
Q

Construct a balanced symbol equation to represent the standard enthalpy of formation of 1.00 of ethanol

A

2C (s) + 1/2O₂ (g) + 3H₂ (g) –> C₂H₅OH (l)

50
Q

When constructing a balanced symbol equation to represent the standard enthalpy of formation, what should the coefficient of the product be?

A

1

51
Q

When constructing a balanced symbol equation to represent the standard enthalpy of formation, how should you represent 1 H atom as a reactant?

A

1/2 H₂ or 0.5H₂

IB Chemistry (3 decks)

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