[CHEM] Unit 11- Kinetics Flashcards

1
Q

In order to react, reactants need to have:

A

Effective collisions

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2
Q

Two things are needed for effective collisions:

A

1) Enough energy

2) Proper orientation (based on polarity)

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3
Q

To react quickly, ionic reactants need to be in the ___ phase

A

Aqueous (aq)- solid ionic reactants don’t break apart

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4
Q

Covalent reactants typically have ___ bonds to break and so react ___

A

More, slowly

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5
Q

Temperature is a measure of the:

A

Average kinetic energy of the particles

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6
Q

A high temp leads to ___ energy, and so ___ particles will collide with sufficient energy

A

Higher, more

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7
Q

A high temp also leads to:

A

Particles moving faster, and so more total collisions will occur

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8
Q

How does concentration affect rate?

A

Higher concentration=faster rates because there are more total collisions

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9
Q

Pressure only affects ___ reactants

A

Gas

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10
Q

How does pressure affect rate?

A

Pressure is caused by the particles colliding with the walls of the container- more collisions will walls will mean more collisions between particles

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11
Q

How does surface area affect rate?

A

Reactions only occur at the surface where the reactants are in contact; therefore, as surface area increases, there will be more total collisions (and in turn more effective collisions)

Trick to remember: Sugar cubes vs powdered sugar

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12
Q

How does one increase surface area?

A

For solids, grind them into small pieces

For liquids, stir

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13
Q

How does a catalyst affect rate?

A

Catalysts reduce the required energy for an effective collision, thereby making more (already existing) collisions effective

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14
Q

T/F: A catalyst is used up during a reaction

A

F

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15
Q

Endothermic=

A

Heat put in (heat is a reactant)

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16
Q

Breaking/forming a bond is endothermic

A

Breaking!

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17
Q

Exothermic=

A

Heat is released (heat is a product)

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18
Q

Breaking/forming a bond is exothermic

A

Forming!

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19
Q

On a PED, if a reaction is endothermic, the ΔH is:

A

Positive

20
Q

On a PED, if a reaction is exothermic, the ΔH is:

A

Negative

21
Q

ΔH is:

A

Heat of reaction, or change of enthalpy

22
Q

How does one tell if a PED is exothermic or endothermic?

A

Products have more energy= Endothermic

Products have less energy= Exothermic

23
Q

The activated complex is:

A

The peak of potential energy; a state between reactants and products

24
Q

Activation energy is:

A

The difference between the PE of the activated complex and the PE of the reactants

25
Q

ΔH is calculated by:

A

PE of products - PE of reactants

26
Q

If a catalyst is added to a PED, what changes?

A

The activation energy is reduced, and the PE of the activated complex is also reduced.

ΔH DOES NOT CHANGE

27
Q

In a reverse PED, the products become the ____ and the reactants become the ___

A

Reactants, products

28
Q

To find the activation energy of a reverse PED, one needs to

A

FInd the different between the PE of the products and PE of the activated complex

29
Q

T/F: In a reverse reaction/PED, the ΔH changes

A

T

30
Q

T/F: The reverse reaction is always the opposite of the normal reaction (in terms of endothermic vs exothermic)

A

T

31
Q

When using Table I for changes in enthalpy, if the coefficients of the reactants/products are changed, then:

A

The ΔH must be changed accordingly (doubled, halved, etc)

32
Q

In terms of enthalpy (ΔH), nature tends to favor ___ energy- ie ___thermic

A

Low, exo

33
Q

Entropy is:

A

Randomness or disorder

34
Q

In terms of entropy (ΔS), nature tends to favor ___ entropy

A

Higher

35
Q

The phase lowest in entropy is:

A

Solid

36
Q

The phase(s) highest in entropy is/are:

A

Gas and aq

37
Q

The phase in the middle in terms of entropy is:

A

Liquid

38
Q

One way to increase entropy is to:

A

Mix the subtances

39
Q

Higher temperature=___ ΔH

A

Higher

40
Q

The equation for Gibbs Free Energy is:

A

ΔG= ΔH- T(ΔS)

TEMPERATURE HAS TO BE KELVIN!!

41
Q

For a reaction to be spontaneous, the ΔG has to be:

A

Negative

42
Q

A positive ΔH (___) and negative ΔS means:

A

Endo; the reaction is ALWAYS positive- therefore it is never spontaneous

43
Q

A negative ΔH (___) and positive ΔS means:

A

Exo; the reaction is ALWAYS negative- therefore it is always spontaneous

44
Q

Both a negative ΔH and ΔS means:

A

The reaction is only spontaneous at LOW temperatures

45
Q

Both a positive ΔH and ΔS means:

A

The reaction is only spontaneous at HIGH temperatures