Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SQA Higher Chemistry Unit 1 > Unit 1(a) - Rates of Reaction > Flashcards

Unit 1(a) - Rates of Reaction Flashcards

1
Q

How can you speed up a reaction?

A
  • Decreasing particle size of solid reactant - increased surface area
  • Increasing concentration of reactant in solution - more particles
  • Increasing temperature of reaction - higher kinetic energy
  • Addition of a catalyst
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How can you follow the rate of a reaction?

A

Measuring changes in conc, mass, and vol of reactants and products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens to the quantity of reactants/products during a reaction?

A

The quantity/concentration of reactants decreases and the quantity/concentration of products increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the formula for average rate of reaction?

A

Av. rate = change in quantity/change in time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the formula for relative rate of reaction?

A

Rel. rate = 1/t

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What kind of reaction can be used to investigate changing concentration and reaction rate?

A

Iodine ‘clock’ reaction

A time lapse occurs before a sudden end point is reached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why are starch and sodium thiosulphate added to the mixture of an iodine clock reaction?

A
  • iodine turns black in presence of starch, so marks an end point of reaction.
  • Thiosulphate changes iodine molecules back into ions, using iodine up before colour forms. Once thiosulphate is all used up, the starch turns blue/black
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the equation for the iodine clock reaction?

A

Hydrogen peroxide + hydrogen ions + iodide ions -> water + iodine molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the relationship between concentration and reaction rate?

A

As the concentration increases, the rate of reaction increases. The concentration is directly proportional to reaction rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What reaction can be used to investigate changing temperature and reaction rate?

A

Oxalic acid and acidified potassium permanganate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the equation for the reaction between oxalic acid and potassium permanganate?

A

Oxalic acid + hydrogen ions + permanganate ions -> magnesium ions + carbon dioxide + water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the relationship between temperature and rate of reaction?

A

As the temperature increases, reaction rate increases. Rate of reaction is not directly proportional to temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

According to collision theory, substances can only react if:

A
  • Their particles collide with each other in the correct orientation
  • Collision have enough energy to allow them to collide with enough force to break existing bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is it important that not all collisions result in a successful reaction?

A

All reactions would be instantaneous. Gentle collisions result in reactant particles bouncing apart unchanged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What experiment can be used to investigate collision theory with respect to concentration, particle size and temperature?

A

Marble (Calcium carbonate) + Hydrochloric acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Marble and hydrochloric acid experiment: vary concentration of HCl

A

The surface of the marble will be hit more often by acid ions (more collisions per second) leading to a faster reaction.
The higher the concentration, the faster the reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Marble and hydrochloric acid experiment: vary particle size of marble

A

Breaking up the solid increases surface area exposed to other reactant. Collisions can only take place on the surface of a reactant.
The smaller the particles, the greater the surface area so the faster the reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Marble and hydrochloric acid experiment: vary temperature

A

Temperature is a measure of the average kinetic energy of particles. Increasing temperature causes reactant particles to move faster, so they collide more often and with greater Ek
The higher the temperature, the more frequent and energetic the collisions, so the faster the reaction

19
Q

What is an exothermic reaction?

A

A chemical change which gives out heat energy to the surroundings

20
Q

Give 3 examples of exothermic reactions

A
  • Combustion of elements/carbon compounds/fuels
  • Displacement of less reactive metals
  • Neutralisation of acids by alkalis and reactive metals
21
Q

In an exothermic reaction, how does the energy of the products compare with the energy of the reactants?

A

The products have less energy than the reactants

22
Q

What is an endothermic reaction?

A

A chemical change which takes in heat energy from the surroundings

23
Q

Give 3 examples of endothermic reactions

A
  • Reaction of steam with hot coke to make water gas
  • Neutralising ethanol acid with ammonium carbonate or sodium hydrogen carbonate
  • Dissolving certain salts in water (ammonium nitrate, potassium nitrate)
24
Q

In an endothermic reaction, how does the energy of the products compare with the energy of the reactants?

A

The products have more energy than the reactants

25
Q

What is enthalpy?

A

A measure of the stored chemical energy in a substance

26
Q

What is the enthalpy change?

A

The energy difference between products and reactants

27
Q

What is the equation for enthalpy change?

A

Change in H = H(products) - H(reactants)

28
Q

What is the term for no enthalpy change?

A

Thermoneutral

29
Q

What is activation energy?

A

The minimum kinetic energy of collisions for a chemical change to occur - to form an activated complex

30
Q

What is an activated complex?

A

An unstable arrangement of atoms formed at the maximum of the potential energy barrier during a reaction

31
Q

What are some characteristics of an activated complex?

A
  • An intermediate stage
  • Highly energetic
  • Only exists for a short time
32
Q

What are energy distribution graphs used for?

A

To explain the effect of changing temperature/concentration/presence of a catalyst on the kinetic energy of particles

33
Q

What is the effect of changing concentration on the kinetic energy of particles?

A

When concentration is increased, all values across the distribution are increased. More particles, so more will have activation energy

34
Q

What is the effect of changing temperature on the kinetic energy of particles?

A

When temperature is increased, the distribution graph is spread out to higher values of kinetic energy. More kinetic energy, so more will have activation energy
NB: total area under graph remains same, so height decreases

35
Q

What is the effect of adding a catalyst on the kinetic energy of particles?

A

The shape and size of the graph does not change as all the particles still have the same activation energy.
However, the activation energy is lowered by the catalyst. Lower activation energy so more will have activation energy

36
Q

What is a catalyst?

A

A catalyst is a substance which increases the rate of reaction by providing an alternate reaction pathway

37
Q

What is the difference between and heterogeneous catalyst and a homogeneous catalyst?

A

Heterogeneous: different state
Homogeneous: same state

39
Q

What is an inhibitor?

A

A substance which raises the activation energy of a chemical reaction

42
Q

Name two photochemical reactions (reactions where light is used to increase the number of particles with activation energy)

A
  • Photosynthesis

* Photography

43
Q

What catalyst is used in the haber process?

A

Iron catalyst

44
Q

What catalyst is used in the Ostwald process?

A

Platinum catalyst

45
Q

What catalyst is used in the contact process?

A

Vanadium pentoxide

46
Q

What catalyst is used in the hydrogenation of oils?

A

Nickel

SQA Higher Chemistry Unit 1 (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions