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IB Chem > Chemistry Topic 5 > Flashcards

Chemistry Topic 5 Flashcards

Kinetics

1
Q

What is the first law of thermodynamics?

A

Energy cannot be created or destroyed. It can only be converted from one form to another

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2
Q

Where is potential energy stored?

A

In the bonds

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3
Q

Where is kinetic energy stored?

A

In the particles

They are always moving

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4
Q

If a reaction is endothermic, is the change in heat positive or negative?

A

Positive because heat is going into the reaction

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5
Q

If a reaction is exothermic, is the change in heat positive or negative?

A

Negative because heat is exiting the reaction

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6
Q

Define specific heat capacity

A

The heat needed to increase the temperature of a unit mass by 1K

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7
Q

Define heat capacity

A

The heat needed to increase the temperature of an object by 1K

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8
Q

What is the difference between specific heat capacity and heat capacity?

A

Specific heat capacity is per unit but heat capacity is for the whole thing

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9
Q

How do you find the enthalpy change (per mole) for reactions?

A

The amount of heat gained or lost by the limiting agent, divided by the number of moles of limiting agent that reacted

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10
Q

If the temperature of a solution in a reaction increases, is heat being gained or lost for that solution?

A

Heat is being gained

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11
Q

In a neutralization reaction, if the temperature decreases, is heat being gained or lost?

A

Heat is being lost

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12
Q

How do you find the total amount of heat produced in a calorimeter when the middle is made of metal?

A

Use the specific heat capacity of the metal to find the amount of heat produced in the metal, and add it to the amount of heat produced for the reaction

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13
Q

What are sources of error in a calorimeter?

A

The metal absorbs some heat and there is space where the air could get out

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14
Q

What is the Standard Enthalpy Change of Formation (Delta Hf)?

A

The enthalpy change associated with forming 1 mole of compound from its elements in their standard states at standard conditions

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15
Q

What is the equation to find the Heat of the reaction using the Enthalpy Change of Formation?

A

Heat of reaction = Summation of Enthalpy Change of Formation for the products - Summation of Enthalpy Change of Formation for the reactants

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16
Q

What substances don’t have a enthalpy change of Formation and why?

A

Diatomic elements that are naturally occurring. This is because they aren’t formed, so there isn’t an enthalpy change of formation

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17
Q

What does Hess’s Law state?

A

The enthalpy change for any chemical reaction is independent of the route, provided that starting conditions, final conditions, reactants and products are the same

Enthalpy change is the same no matter how you get there

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18
Q

When Using Data to calculate the enthalpy change for chemical reactions

What do you do to the original enthalpy change if you have to flip the equation?

A

You make it the opposite sign (negative/positive)

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19
Q

When Using Data to calculate the enthalpy change for chemical reactions

What do you do to the enthalpy change if you have to multiply the equation by 2?

A

Multiply it by 2!

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20
Q

Define bond enthalpy

A

The amount of energy needed to break 1 mole of bonds in gaseous molecules under standard conditions

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21
Q

Why does the data booklet have average bond enthalpies?

A

Because the bond energy is different depending on the molecule, and how many bonds have already been broken/formed

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22
Q

Why might the delta H of reaction we calculate through adding bond enthalpies different from what is in the data booklet?

A

Because the one in the data booklet is taken from the average of many different molecules

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23
Q

What is the formula to calculate Delta H reaction through bond enthalpies?

A

Delta H reaction = sum of Enthalpy from broken bonds - sum of Enthalpy from formed bonds

24
Q

Define First ionization energy

A

The minimum amount of energy required to remove 1 mole of electrons from 1 mole of gaseous atoms

25
Q

Which is always bigger, the first or second ionization energy, and why?

A

The second is always bigger because after the first occurs, the atoms get smaller, causing the electrons to have a stronger force holding them in

26
Q

Define 1st electron affinity and state if it is exothermic or endothermic

A

The enthalpy change when 1 mole of gaseous atoms attracts 1 mole electrons. It is exothermic because adding more electrons makes an atom more stable, giving it a negative electron affinity

27
Q

Is the 2nd electron affinity endo or exothermic, and is it positive or negative?

A

It is endothermic and positive because it is a negatively charged electron being added to a negative ion

28
Q

Define bond enthalpy

A

Energy needed to break 1 mole of bonds of gaseous molecules under standard conditions

29
Q

Define lattice enthalpy (IB definition)

A

Enthalpy change when 1 mole of a solid ionic compound is separated into its gaseous ions under standard conditions

30
Q

Are lattice enthalpies (under IB definition) always endothermic or exothermic?

A

Endothermic because it requires energy to break bonds

31
Q

How is the AP definition different from the IB definition for lattice enthalpy?

A

AP - the ions are put together
IB - the compound is split into ions

32
Q

Define enthalpy of atomization

A

Energy change when 1 mole of gaseous atoms is formed from 1 mole of an element in its standard state

33
Q

Which elements don’t have enthalpies of atomization?

A

Elements that are gasses in standard states

34
Q

What is a Born-Haber Cycle?

A

A cycle that shows the energy for the formation of an ionic solid using Hess’s Law

35
Q

What do you label the left side of the Born-Haber Cycle?

A

Potential Energy

36
Q

What do you do for ionization energies if the Born-Haber Cycle involves a metal that forms a +2 ion?

A

You need to find/know 1st and 2nd ionization energy

37
Q

What do you do for ionization energies if the Born-Haber Cycle involves 2 metal ions (of the same element) that are both +1?

A

You multiply the 1st ionization energy by two because two separate moles of ions are losing 1 mole of electrons

38
Q

What three factors increase entropy?

A
  1. Change in state (s->l->g)
  2. Number of particles/dissociation (NaCl(s) -> Na(aq)+ + Cl(aq)-)
  3. Number of moles of gas
39
Q

What is the equation to find the delta S?

A

Delta S rxn = products - reactants

40
Q

What are the units for delta S?

A

J/mole K

41
Q

What does delta S mean?

A

The change in entropy

42
Q

What are two equations to find delta G?

A

Delta G = (Delta H) - (T)(Delta S)
or
Delta G = products - reactants

43
Q

What does a positive delta S mean and is it favorable?

A

Entropy is increasing and yes it is favorable

44
Q

What does a negative delta S mean and is it favorable?

A

Entropy is decreasing, no it is not favorable

45
Q

Are exothermic or endothermic reactions favorable?

A

Exothermic

46
Q

When are reactions at equilibrium?

A

When delta G is 0

47
Q

When are reactions not spontaneous?

A

When delta G is positive

48
Q

When are reactions spontaneous?

A

When delta G is negative

49
Q

Does the enthalpy arrow point towards or away from the heat?

A

Towards

50
Q

What substances have a delta G of 0?

A

Things that are elements in their standard states

51
Q

What must you always say when commenting about a delta G value?

A

That the reaction is only spontaneous/no spontaneous at standard conditions

52
Q

What does it imply when the delta S is very small?

A

That the delta H and delta G are very close together

53
Q

What compounds will give the greater lattice enthalpy?

A

Small ions within the compounds that have greater charges

54
Q

List the typical steps of a Born-Haber Cycle

A
  1. Atomization of the metal
  2. Bond enthalpy of nonmetal
  3. First (sometimes + second) ionization of metal
  4. First (sometimes + second) electron affinity of nonmetal
  5. Lattice enthalpy
55
Q

What way must the arrow point on a Born-Haber Cycle for lattice enthalpy?

A

Up

56
Q

Why are second electron affinities positive and lead to more energy?

A

You are adding a negative electron to a negative ion which will cause some repelling

57
Q

What sign is lattice enthalpy according to the IB definition?

A

Positive, it is endothermic

IB Chem (4 decks)

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