Chemsitry test Rate Of Reaction

Question 1

Equation for calculating average rate

Answer 1

Rate = Change in amount of product/ time taken

OR

Rate = Change in amount of reactant/time taken

Question 2

How does a chemical reaction occur?

Answer 2

there must be:
- enough energy greater to or equal to the activation rate for the reaction
- the reactants to collide

Question 3

Activation Energy

Answer 3

It is the minimum amount of energy particles must possess if they are to react when they collide.

Question 4

What is the rate of reaction?

Answer 4

The rate of a reaction is a measure of the number of successful collisions per unit time.

Question 5

What does the gradient tell us?

Answer 5

The steeper the gradient the faster the rate of reaction

Question 6

How does the gradient typically change during a reaction?

Answer 6

It starts off steep than the gradient decreases until the graph plateaus and the reaction stops.

Question 7

Describe collusion theory

Answer 7

Collision theory states that in order for a chemical reaction to occur there must be energy greater or equal to the activation energy and the reactants must collide.

Question 8

Activation Energy

Answer 8

The minimum amount of energy, particles must possess of for them to react when they collide.

Question 9

Why does the rate of reaction decrease during the reaction?

Answer 9

As there are fewer reactants particles, there are fewer collisions between reactant per unit time and therefore fewer successful collisions per unit time.

Question 10

How does surface area affect the rate of reaction?

Answer 10

1. The smaller the pieces of solid reactant, the faster the rafters of reaction.
2. Smaller pieces have a larger surface area than larger pieces with the same total mass.
3. More particles of the solids reactant are in contact with particles of the other reactant
4. Therefore there are more collisions between reactant particles per unit time, so the rate of reaction increases.

Question 11

How does concentration affect the rate of reaction?

Answer 11

1. Increasing the concentration of a reactant in solution means that there are more particles of that reactant in a given volume.
2. Therefore there are more successful collisions between reactant particles per unit time.
3. the rate of reaction increases.

Question 12

How does temperature affect the rate of reaction?

Answer 12

1.The higher the temperature the faster the rate of reaction
2. At a higher temperature, reactant particles have more kinetic energy and so move around faster.
3. This results in more collisions per unit time between reactant particles.
4. As well, more particles will collide with energy equal to or greater than the activation energy, so more of the collision will be successful.

Question 13

How does pressure affect the rate of reaction?

Answer 13

Increasing the pressure means that there are more reactants particles particles in a given volume.
As a result, there are more collisions between reactant particles per unit time, so the rate of reaction increases.

Question 14

How do catalysts affect the rate of reaction?

Answer 14

Catalysts provide an alternative reaction pathway with a lower activation energy.
This means that more collisions will have energy equal to or greater than the activation energy, so more of the collisions will be successful.

Question 15

What are catalysts?

Answer 15

A catalyst is a substance that speeds up the rate of a reaction but is chemically unchanged at the end. It is not used up in the reaction.

Question 16

Marble Chips Experiment Method

Answer 16

1. Set up the apparatus and clamp the gas syringe in place.
2. Measure the hydrochloric acid into the conical flask and add the marble chips to the conical flask
3. Quickly replace the bung and start a timer. Swirl frequently.
4. Record the time taken for 50cm3 of gas to be produced.
5. Repeat the experiment with the same marble chips but different concentrations of acid.

Question 17

Word equation for marble chips reaction (surface area)

Answer 17

Calcium carbonate + hydrochloric acid —> calcium chloride + water + carbon dioxide.

Question 18

Symbol equation for marble chips reaction

Answer 18

CaCO3 + 2HCl —> CaCl2 + H2O + CO2

Question 19

Method for Marbel chips experiment (surface area)

Answer 19

1. Place a measuring cylinder upside down in the water trough. The measuring cylinder should be completely full of water.
2. Clamp the measuring cylinder in place.
3. Measure the hydrochloric acid into the conical flask.
4. Add large ,arable chips to the conical flask, quickly replace the bung and starter the timer.
5. Swirl well and record the volume of gas produced every 10 seconds.

Question 20

Why is the mixture cloudy?

Answer 20

The chemical reaction is producing sulfur which is precipitate and turns the mixture cloudy when produced.