Rates of reaction

Question 1

one general way to measure the rate of a reaction

Answer 1

Measure how fast one of the reactants is used up

Question 2

Another general way to measure the rate of a reaction

Answer 2

Measure how fast one of the products is made

Question 3

5 main factors that are important when studying rates of chemical reactions

Answer 3

Concentration( of solutions), temperature, surface area(for solids), catalyst, pressure (for gases)

Question 4

For a reaction to occur what must reactant particles do

Answer 4

Collide with each other

Question 5

What is the activation energy

Answer 5

The minimum amount of energy required for a reaction to take place

Question 6

More energetic collisions allow bonds to be broken between reactant particles true or false?

Answer 6

True

Question 7

Rates of chemical reactions are ? up if the ? of collision with greater than the activation energy ?

Answer 7

Speeded up, frequency, increases

Question 8

If particles do not reach the activation energy what happens

Answer 8

They will still collide but will bounce off each other not successfully collide

Question 9

Collision theory is the idea that a reaction can only occur when two particles collide together with enough energy - it has to be equal or more than the activation energy

Answer 9

True

Question 10

What does increasing the concentration of reactants/ liquids in a solution do

Answer 10

It means there are more particles of reactants in the same volume which leads to more frequent and therefore successful collisions and a faster rate of reaction.

Question 11

What happens when all the reactants have been used up

Answer 11

The reaction stops anything that was happening stops eg if acid was fizzing once all the reactants had been used up it would stop fizzing and become clear.

Question 12

The reaction between calcium carbonate (marble chips) and hydrochloride acid - what two methods could be used to measure the rate of this reaction

Answer 12

Gas collection( product)
Mass loss (reactant)

Question 13

Assessed practical how does surface area affect the rate of reaction?- tests how many cm cubed of carbon dioxide there are in (max) 180 seconds and sees how it varies between the different sizes of marble chips

Answer 13

The larger the surface area (to vol ratio) the higher the rate of reaction casue there are more particles so more of them to collide so more frequent successful collisions so the rate of reaction is faster

Question 14

Assessed practical- how temp affects the rate of reaction between hydrochloric acid and sodium thiosulphate - add sodium thiosulphate to hydrochloric acid, and heat it at different temperatures eg: 20,30,40 etc and place it on top of a black cross and start the timer and when u can no longer see the black cross from looking straight into the solution, stop the timer

Answer 14

The higher the temperature the higher the reaction rate (and steeper the concentration gradient) -

Question 15

Explain answer to Q 14 using collision theory

Answer 15

Particles move faster because of the higher temperature meaning that they will collide more frequently and they have more energy so more particles successfully collide, giving more frequent successful collisions causing a reaction.

Question 16

Theory on SA and reaction rate : crushing up a solid into a powder ? its surface area to ? ratio, meaning that there is a ? area of contact between the solid and other reactant and more ? collisions, so the ? the SA of a solid the ? the rate of reaction

Answer 16

Increases, volume, larger, frequent, larger, faster

Question 17

How to work out rate of reaction:

Answer 17

Pick a multiple of 10, eg: 1000, so then 1000/ time in seconds

Question 18

Temperature and reaction rate theory: increasing temp of a reaction increases ? energy of the particles, meaning particles move ? And ? more frequently, also more of the collisions have energy exceeding the ? energy so more successful ? causing a ?

Answer 18

Kinetic, faster , collide, activation, collisions, reaction

Question 19

What happens in a low temperature then

Answer 19

Particles don’t move as fast, less frequent collisions, less collisions exceeded activation energy so less successful collisions

Question 20

Pressure and reaction rate (for gases only): Changing pressure has no effect on reactions with only ? and liquids, as the particles in these states are already ? together, but changing pressure of a reaction with ? has a similar effect to changing the concentration of a solution with ? Increadjng the ? Of a gas means there are more gas ? in a certain? Meaning they will collide more ? And rate of reaction will ?

Answer 20

Solids, close, gases, liquids, pressure, particles, volume, frequently, increase

Question 21

How does surface area affect the rate of reaction: basically :

Answer 21

Have a conical flask with marble chips and hydrochloric acid in the bottom with a bunt and delivery tube running from there to a trough of water. in trough of water is a measuring cylinder ( secured by a clamp) full of water under which u have to put the delivery tube . What will happen is u set up all of this, put marble chips and hydrochloric acid in the bottom of the conical flask and then put the bung and delivery tube back on very quickly.

Question 22

What is a catalyst?

Answer 22

A substance that’s speeds up a reaction without being used up

Question 23

How do catalysts make reactions faster?

Answer 23

They provide an alternative route for the reaction with a lower activation energy

Question 24

Catalysts are designed to have a large surface area true or false

Answer 24

True

Question 25

What type of metals and metal compounds are often good catalysts?

Answer 25

Transition

Question 26

What does the gradient of the line on a graph mean with reactions?

Answer 26

Measures the rate of reaction

Question 27

At the start of a reaction why is the gradient so steep

Answer 27

Casye the reaction is at its fastest point as the reactants are at their greatest concentration

Question 28

At the middle of a reaction why is the gradient less steep

Answer 28

More of the reactants have been used up so the concentration of reactants is lower

Question 29

At the end of a reaction why is the gradient nothing

Answer 29

Because the reaction has stopped, so no more product is being made so it is a straight line