Rate of reactions

Question 1

How is the rate of reaction found

Answer 1

The rate of a chemical reaction can be found by measuring the amount of a reactant used or the amount of product formed over time.

Question 2

Rate of reaction equation

Answer 2

1/t

Question 3

Apparatus used to measure volume of gas

Answer 3

Gas syringe

Question 4

What are successful collisions ?

Answer 4

Successful collisions are ones that result in a reaction, and they take place when
reactant particles collide with the activation energy.

Question 5

What are unsuccessful collisions ?

Answer 5

Unsuccessful collisions are ones that do not result in a reaction as the particles collide
with less than the activation energy

Question 6

What is the activation energy?

Answer 6

Activation energy: is the minimum energy required for a reaction to occur

Question 7

A number of factors/ reaction conditions can be changed in a reaction (4)

Answer 7

A Concentration
B Surface area
C Temperature
D Catalysts

Question 8

How does concentration affect a reaction ?(3)

Answer 8

At a low concentration there are few particles in a given space so there are few successful collisions
As the concentration is increased there are more particles in the same volume so there will be more collisions.
In a fixed period of time there are more collisions with the activation energy therefore rate of reaction increases

Question 9

How does temperature affect a reaction ?(2)

Answer 9

• In a chemical reaction when the temperature is increased the reacting particles gain energy and move faster.
• As the particles are moving faster there are more successful collisions in a given time therefore faster rate of reaction.

Question 9

How does a catalyst affect the rate of reaction ?(2)

Answer 9

• Catalysts increase this rate of reaction by lowering the activation energy of a reaction.
• This means that in a catalytic reaction when particles collide more of them have sufficient energy to overcome the energy barrier to form products and the reaction is faster.

Question 10

How does surface area affect the rate of reaction?

Answer 10

• As surface area is increased more particles are exposed so there will be more collisions.

Question 11

What is the activation energy ?

Answer 11

Activation energy is the minimum energy required for a reaction to take place.

Question 12

Reaction between metal and a dilute acid and product produced that can be measured for the rate of reaction

Answer 12

Metal + hydrochloric acid —> metal chloride + hydrogen

Volume of hydrogen measured

Question 13

Reaction between calcium carbonate (marble chips) reacting with dilute hydrochloric acid and what product produced can be measured for rate of reaction

Answer 13

CaCO3 + 2HCl —> CaCl2 + H2O + CO2

Produces carbon dioxide gas to be measured

Question 14

Catalytic decomposition of hydrogen peroxide solution (H2O2) And product produced that can be measured

Answer 14

2H2O2 —> 2H2O + O2

Produces oxygen gas

Question 15

Product produced by reaction between sodium thiosulfate solution and hydrochloric acid

Answer 15

Produces precipitate of Sulfur, making the solution go cloudy

Question 16

Effect of particle size on reaction rate (4)

Answer 16

• Smaller particles have a much larger surface area-to-volume ratio.
• There is more Contact between the surface of the smaller marble chips and the acid
• This causes a greater rate of reaction
• The steeper initial slope of the curve for small marble chips indicates that the mass is decreasing more quickly

Question 17

What does cotton wool do in the reaction between calcium carbonate and hydrochloric acid ?

Answer 17

Stops any liquid loss from the flask during effervescence

Question 18

Name the catalyst used to decompose hydrogen peroxide

Answer 18

Manganese (iv) oxide

Question 19

Draw the apparatus for measuring gas volume (5)

Answer 19

• Reaction mixture in Contact with each other in conical flask
• Delivery Tube into conical flask
• Bung
• Gas syringe
• Stopwatch

Question 20

What metals and their compounds are normally used as catalysts ?

Answer 20

Transition metals

Question 21

Explain the catalytic action in terms of providing an alternative reaction pathway of lower activation energy (a graph with a line higher than original bc of catalyst ) (4)

Answer 21

• Gas Volume starts at Zero
• Gas Volume is higher at every time
• The line on the graph levels off earlier
• The line ends at same final gas volume

Question 22

Name alternative methods to monitoring the rate of reaction aside from volume of gas (2)

Answer 22

• Mass of the reaction mixture as gas is released

- Time for reaction to stop (Fizzing)

Question 23

Describe the catalytic decomposition of hydrogen peroxide solution

Answer 23

2H2O2 —> 2H2O + O2

Question 24

How is mass an indicator of rate of reaction (2)

Answer 24

• Mass is ‘lost’ during this reaction because carbon dioxide escapes from the reaction vessel,
• Recording the loss in mass over a certain period of time at regular intervals using an electronic balance gives an indication of the rate of reaction

Question 25

How to plot graph showing effect of particle size on reaction rate

Answer 25

• Time / s along the bottom

- Mass / g along the side

Question 26

How does particle size affect the volume of gas produced (3)

Answer 26

• Volume of gas produced increased more rapidly initially when small marble chips are used
• Graph starts and ends at the same Gas Volume since the same mass of marble chips and Volume and concentration of HCl are used
• the curve is steepest at the start which indicates the reaction is fastest at the start and gradually gets slower as it proceeds. This is because the reactants are being used up and so the rate of reaction decreases

Question 27

Anomaly definition

Answer 27

An anomaly is a piece of data that does not match the pattern shown in the rest of the investigation