Chemical Equilibrium Flashcards

1
Q

What do 2 Mg atoms react with 1 O2 molecule to form?

A

2 molecules of magnesium oxide

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2
Q

Can you turn MgO back into magnesium and oxygen? What does this mean?

A

Very hard to turn MgO back into magnesium and oxygen

Reaction goes to completion

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3
Q

Do all reactions go to completion?

A

no

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4
Q

If a reaction does not go to completion what do you usually call it?

A

reversible

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5
Q

N2 + 3H2 -> 2NH3 What process is this?

A

Haber process

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6
Q

What is a reversible reaction?

A

a reaction takes place both in the forward and backward directions

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7
Q

is the Haber process reversible?

A

Yes, some of the ammonia formed decomposes and becomes Nitrogen and hydrogen again

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8
Q

What is chemical equilibrium?

A

a balance where the rate of the forward reaction is equal to the rate of the backward reaction

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9
Q

What is the conc. of ammonia at the beginning of the Haber process?

A

0

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10
Q

What happens to the conc. of ammonia as the Haber process reaction proceeds?

A

As the reaction proceeds, the conc. of N2 and H2 decreases and the conc. of NH3 increases.

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11
Q

What happens when the rate of production of NH3 equals its rate of decomposition?

A

When the rate of production of NH3 equals its rate of decomposition the reaction has reached equilibrium

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12
Q

What happens to the conc. of all species in the Haber process at equilibrium?

A

the conc. of all species remains constant

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13
Q

What is dynamic equilibrium?

A

Constantly “moving”

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14
Q

What is Le Chatelier’s Principle?

A

If a “stress” is applied to a system at equilibrium, the system readjusts itself to relieve the stress applied

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15
Q

What does the term “stress” mean in Le Chatelier’s Principle?

A

Stress is a change in reaction conditions:

  • Conc of reactants/products
  • Temp.
  • Pressure
  • Catalyst
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16
Q

What happens if we change the conditions of a reaction at equilibrium?

A

the reaction readjusts itself to relieve the stress

17
Q

How does Le Chatelier’s Principle work with pressure?

A

Le Chatelier’s Principle predicts that in all gaseous reactions, an increase in pressure will favour the reaction which reduces the volume (i.e. towards the side with the smaller number of molecules

18
Q

What does pressure only have an effect on?

A

Gaseous reactions

19
Q

If there are the same number of molecules on both sides of the reaction, how will a change in pressure affect it?

A

a change in pressure will have no effect on the equilibrium

20
Q

What happens when the temperature of the reaction is changed?

A

The reaction shifts itself to relieve the “stress”

21
Q

2NO2(g) N2O4(g) What type of reaction is the forward reaction?

A

exothermic (produces heat)

22
Q

What does changing the concentration of one of the reactants do?

A

shifts the reaction to the right (forwards) to relieve the stress

23
Q

What does changing the concentration of the product do?

A

shifts the reaction to the left (backwards) to relieve the stress

24
Q

What catalyst is in the Haber process?

A

Iron catalyst

25
Q

Where is the Haber process used?

A

Product made at IFI plant in Cobh, Cork

26
Q

What type of forward reaction is in the Haber process?

A

exothermic (deltaH = -92.4kJmol-1

27
Q

What is the pressure in the Haber process?

A

4 molecules on left, 2 on right
Increase pressure will favour production of ammonia
Keeping pressure high is expensive
200 atmospheres most cost effective and safe

28
Q

What is the temperature in the Haber process?

A

Forward reaction is exothermic
Lowering temp. will favour production of ammonia
Too slow at very low temps
500 degrees celsius temp

29
Q

Haber process/chemical equilibrium equation

A

For reactions in the form: aA + bB -> cC + dD

Kc = [C]c[D}d over [A]a[B]b

30
Q

What is the empirical formula?

A

The empirical formula gives the simplest whole number ratio of the numbers of the different atoms present in the molecule. (divide by Ar and get ratio) (molecular formula is a simple multiple of the empirical formula)

31
Q

What is a mass spec.?

A

Used to analyse blood of race horses for drugs, identify substances

32
Q

What is AAS?

A

Used to analyse water samples for heavy metals (Cd, Hg, Pb)

33
Q

What is a GC?

A

Used with MS in drug testing also blood alcohol levels

34
Q

What is HPLC used for?

A

Used to separate less volatile mixtures e.g. growth promoters in meat.

35
Q

What is IR spec.used for?

A

Used to identify functional groups and identify drugs

36
Q

What is UV spec. used for?

A

Quantitative used to find amount of org. subs. e.g. drugs