3.2.2, 2.1.3 Reaction rates

Question 1

how do you measure the rate of a chemical reaction

Answer 1

rate = change in concentration/time

Question 2

what are the units for working out rate

Answer 2

mol dm⁻³ s⁻¹ = mol dm³/ s

Question 3

how is rate worked out on a concentration-time graph

Answer 3

the gradient of this graph is equal to rate.
The gradient can be measured at any point using a tangent

Question 4

What factors can inflience the rate of reaction

Answer 4

• concentration
• pressure
• surface area
• temperature
• catalyst

Question 5

In order for a reaction to happen what must the particles collide with

Answer 5

• Sufficient energy (greater than the Ea)
• the correct orientation

Question 6

what is the difference between concentration and pressure

Answer 6

concentration is only used for solutions
pressure is only used for gases

Question 7

What happens to rate of reaction if you increase the concentration

Answer 7

Higher concentration means more particles in the same space
Therfore there are more frequent collisions and rate increases

Question 8

What happens to rate of reaction if you increase the pressure

Answer 8

Higher pressure means that there are the same number of particles in a smaller space
Therefore there are more frequent collisions and rate increases

Question 9

What happens to rate of reaction if you increase the surface area

Answer 9

When the surface area is increased, there are more particles available to collide
therefore there are more frequent collisions and rate increases

Question 10

What happens to rate of reaction if you increase the temperature

Answer 10

when temperature is increased, particles have more energy and move faster. so there are more frequent collisions and more forceful collisions so rate increases

Question 11

What happens to rate of reaction if you add a catalyst

Answer 11

The addition of a catalyst provides an alternative route with a lower activation energy and so there are more successful collisions and rate increases

Question 12

outline an experiment that monitors the production of gas using gas collection

Answer 12

(rate of reation for the decomposition of hydrogen peroxide H₂O₂)
1. hydrogen peroxide us added to the conical flask and the bung is replaced
2. the initial volume of gas in the measuring cyclinder is recorded.
3. Manganese dioxide MnO₂, catalyst is then quickly added to the conical flask and the bung is replaced
4. a stopclock is started
5. The volume of gas in the measuring cylinder is recorded at regular intervals until the reaction is completed
6. the reaction is complete when no more gas is produced

A gas syringe can be used instead of a measuring cylinder
Could also monitor the rate of reaction between calcium carbonate and hydrochloric acid

Question 13

list the apparatus used to monitor the prduction of gas using gas collection in an experiment

Answer 13

• conical flask
• bung connected to a delivery tube
• gas syringe
• clamp stand
• clamp
• boss
• stopwatch