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Chemistry A2 > F325 - Rates, Equilibrium and pH > Flashcards

F325 - Rates, Equilibrium and pH Flashcards

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0
Q

What is the order of a reaction?

A

The power to which the concentration of a reactant is raised in the rate equation.

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1
Q

What is meant by the term rate of reaction?

A

The amount in moles of a reactant which is used up or product which is formed in a given time.

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2
Q

What does a zero order of reaction indicate?

A

The reactant does not affect the rate.

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3
Q

What does a first order of reaction indicate?

A

The reactant concentration is directly proportional to the rate.

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4
Q

What does a second order of reaction indicate?

A

The square of the reactant concentration is directly proportional to the rate.

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5
Q

What is meant by the term rate constant?

A

The proportionality constant, k, in a rate equation. Rate = k[A][B]

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6
Q

What is the rate determining step?

A

The slowest step in a reaction mechanism.

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7
Q

What is meant by the term half-life?

A

The time taken for the concentration of a reactant to fall to half its original value.

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8
Q

For a first order reaction what is independent of the concentration?

A

Half-life

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9
Q

What is needed for the experimental determination of the rate equation using the initial rates method?

A

Separate experiments using different concentrations of one of the reactants. The time is measured and then:
rate = concentration/time

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10
Q

What affects the rate constant of a reaction?

A

Temperature

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11
Q

Why does pressure not affect the rate constant?

A

It changes the concentrations of the reactants. (Change in volume!)

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12
Q

How does increasing the temperature affect the rate constant?

A

Increases k

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13
Q

What does the rate equation tell you about a multi-step reaction mechanism?

A

The species and the number of them which take place in the rate determining step.

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14
Q

How is the overall order of a reaction determined?

A

The sum of the orders with respect to the individual reactants.

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15
Q

What is Le Chatelier’s principle?

A

When any conditions affecting the position if equilibrium are changed, then the position of equilibrium will shift to minimise that change.

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16
Q

How will changing the concentration affect the position of equilibrium?

A

Increase concentration: shift to the side where the increase did not take place

Decrease concentration: shift to the side where the decrease did take place

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17
Q

How will changing the pressure affect the position of equilibrium?

A

Increase pressure: shift to the side with the fewer number of moles (of gas)

Decrease pressure: shift to the side with more moles (of gas)

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18
Q

How will changing the temperature affect the position of equilibrium?

A

Increase temperature: shift in the direction of the endothermic reaction

Decrease temperature: shift in the direction of the exothermic reaction

19
Q

How is Kc calculated?

A

Kc = [RHS or products]/[LHS or reactants]

20
Q

How does increasing the temperature affect the value of Kc?

A

Endothermic reaction: Kc increases

Exothermic reaction: Kc decreases

21
Q

What factors do not affect the value of Kc?

A
  • Concentration
  • pressure
  • catalysts
22
Q

Larger Kc values would indicate what about a reaction?

A

High theoretical yields

23
Q

What is a meant by Brønsted-Lowry acid?

A

A species which can donate a proton.

24
Q

What is meant by a Brønsted-Lowry base?

A

A species which can accept a proton.

25
Q

What does the term amphoteric mean?

A

A substance which can behave as an acid or a base, depending on the conditions.

26
Q

What is meant by the term conjugate acid-base pair?

A

The acid in the forward reaction and the base in the reverse reaction are a pair (or vice versa).

27
Q

What is a strong acid?

A

A proton donor which fully dissociates.

28
Q

What is a weak acid?

A

A proton donor which only partially dissociates.

29
Q

What does the acid dissociation constant show and how is it calculated?

A

The extent of acid dissociation.

Ka = [H+][A-]/[HA]

30
Q

How is pKa calculated?

A

pKa= -logKa

31
Q

How is pH calculated?

A

pH= -log[H+]

32
Q

How is hydrogen ion concentration calculated given the pH of a solution?

A

[H+] = 10^-pH

33
Q

What is the ionic product of water?

A

Kw = [H+][OH-] = 1.00 x 10^-14 (constant)

34
Q

What are the two assumptions made to simplify the Ka calculation?

A
  1. Assume that [H+] = [A-]
  2. Assume that [HA] is approx equal to the concentration of the acid (only a very small number of molecules have dissociated)
35
Q

What is meant by the term buffer solution?

A

A system that minimises pH changes on addition of small amounts of an acid or base.

36
Q

What is needed to make a buffer solution?

A

A weak acid and a salt of the weak acid.

37
Q

What are the products formed between a weak acid and a base?

A

Salt (of the weak acid) and water

38
Q

In an acidic buffer solution what happens on the addition of a small amount of acid?

A

H+ ions react with salt ions and shift equilibrium to the left (produces more of the weak acid).

39
Q

In an acidic buffer solution what happens on the addition of a small amount of alkali?

A

OH- ions react with the weak acid and shift the equilibrium to the right (producing more hydrogen ions).

40
Q

How is the buffer ratio calculated?

A

Ka/[A-] = [H+]/[HA]

41
Q

How does the carbonic acid-hydrogencarbonate buffer work in blood pH levels?

A
  • haemoglobin reacts with oxygen
  • oxygen released in tissues so aerobic respiration can take place
  • carbon dioxide and water produced
  • they are in equilibrium which forms hydrogen ions
  • hydrogencarbonate ion reacts with hydrogen ions to produce more carbon dioxide
  • carbons dioxide carried back to lungs and breathed out
42
Q

What needs to be considered when drawing an acid-base titration pH curve?

A
  • strength/pH of starting solution
  • are concentrations of acid and base equal (this means it’ll be one to one and use the same volume!)
  • where does the vertical section go (volume + make sure it is vertical)
  • strength/pH of added solution
43
Q

How is a suitable indicator chosen?

A

The end point or pH range of the indicator is in the vertical section of the pH curve or is within the equivalence point of the titration.

44
Q

What is the enthalpy change of neutralisation?

A

Enthalpy change to produce one mole of water from the reaction of an acid and an alkali

45
Q

What is the relationship between pH and pOH?

A

pH + pOH = 14

Chemistry A2 (6 decks)

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