C2.4 Rates of reaction Flashcards Preview

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Flashcards in C2.4 Rates of reaction Deck (17)
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1

What are the 4 things that increase the rate of a reaction?

- Increased temperature
- Adding a catalyst
- Increased concentration/pressure
- Surface area of solids

2

What is the 'activation energy' of a reaction?

The minimum amount of energy particles must have to react.

3

Chemical reactions only occur when...

...reacting particles collide with each other with sufficient energy.

4

How does increasing temperature increase the rate of reaction?

- It increases the speed of the reacting particles
- So they collide more often and with more energy

5

How does increasing the concentration/pressure of reacting solutions/gases increase the rate of reaction?

- There are more particles of the reactants within a certain area
- Meaning they are more likely to collide, meaning more frequent collisions

6

How does increasing the surface area of solid reactants increase the rate of reaction?

- The particles around the solid reacting with it will have a larger area to collide with
- Meaning there will be more frequent collisions

7

Define a 'catalyst'.

A substance which increases the speed of a reaction without being used up or changed

8

How does using a catalyst increase the rate of a reaction?

It gives the reacting particles a surface to stick to, increasing the number of successful collisions.

9

What are the advantages of using catalysts in the industry?

- They increase the rate of reaction, meaning a plant doesn't have to operate as long to produce the same amount of product
- A catalyst will allow a reaction to work at a much lower temperature, this will reduce the amount of energy needed for the same amount of product.
- They are never used up or changed in the reactions so they can be reused

10

What are the disadvantages of using catalysts in the industry?

- They are expensive to buy
- Different reactions need different catalysts which will all have to be bought
- Catalysts stop working easily from impurities, so the reaction environment needs to be kept clean.

11

Name 3 ways to measure the rate of reaction.

- Precipitation
- Change in mass
- The volume of gas given off.

12

How is precipitation used to measure the rate of reaction?

- This is used when the product of a reaction is a precipitate which clouds the solution.
- Observe a mark through the solution and time how long it takes to disappear.
- The quicker the mark disappears, the quicker the reaction.

13

What is a disadvantage in using precipitation to measure the rate of reaction?

It is very subjective - different people might not agree on the exact point the mark disappears at.

14

How is change in mass used to measure the rate of reaction?

- This is used with a reaction that produces gas (usually)
- As the gas is released the mass disappearing is easily measured on a mass balance.
- The quicker the reading on the balance drops, the faster the rate of reaction.

15

How is the volume of gas given off used to measure the rate of reaction?

- A gas syringe is used to measure the volume of gas given off.
- The more gas given off during a given time interval, the faster the rate of the reaction.

16

What is the unit of concentration in solutions?

mol/dm3 (cubed)

17

When do gases have the same number of molecules?

When they have equal volumes at the same temperature and pressure.