Chapter 8- Rates, Equilibrium and organic chemistry

Question 1

How do you find out the rate of a chemical reaction?

Answer 1

By monitoring the amount of reactants used up over time

Question 2

What is the equation for finding the rate of reaction?

Answer 2

Quantity of reactant used/ time or

Quantity of product formed/ time

Question 3

What can the gradient on a graph tell you about the reaction time?

Answer 3

It tells you the reaction time. The steeper the line the faster the reaction

Question 4

How do you calculate the rate of reaction from a graph?

Answer 4

Draw the hypotenuse on the curved line and work out its gradient by dividing the length of the y axis by the x axis (opposite by the adjacent)

Question 5

How do particles react?

Answer 5

By colliding with a certain amount of energy

Question 6

What is the activation energy of a reaction?

Answer 6

The minimum amount of energy that particles must have in order to react.

Question 7

What happens if the surface area to volume ratio of any solid reactants is increased what happens?

Answer 7

It increases the frequency of collisions between reacting particles. A larger surface are doesn’t increase the amount of reactions but simply increases the frequency of colliding particles. There are more particles in the same volume of water.

Question 8

How do you measure the decreasing mass of a reaction mixture in a practical experiment?

Answer 8

Hydrochloric acid is put into a flask, place the flask on a weighing scale, then calcium carbonate is added and then a piece of cotton wool will be placed loosely over the flask.
Record the weight every 30s until there is no further change in mass

Question 9

Practical experiment for the rate gas given off.

Answer 9

Attach a gas syringe to a clamp, connect the gas syringe to the bung, measure hydrochloric acid out and put into the flask attach the tube to the flask and the syringe. Take the calcium carbonate and put it in with the hydrochloric acid and attach the bung, take readings every 30s from the gas produced until no more.

Question 10

Measuring the decreasing light passing through a solution?

Answer 10

Take sodium thiosulfate and pour it into a flask, take water and put it into another flask, in another flask have hydrochloric acid place a clean flask on paper with a cross. Combine all the substances and start timing. Tome until you cant see a cross anymore.

Question 11

What is collision theory?

Answer 11

Particles must collide with a certain minimum energy to react

Question 12

How does surface area affect the rate of reaction?

Answer 12

The rate of chemical reaction increases if the surface area to volume ratio increases.
It increases the frequency of the particles colliding.

Question 13

How does increasing temperature increase the rate of reaction?

Answer 13

Particles collide more frequently and more energetically, more of the collisions occurring in a given time results in a reaction because a higher proportion of particles have energy greater than the activation energy

Question 14

How does concentration affect the rate of reaction?

Answer 14

Increasing the concentration increases the frequency of collisions between particles, and so increases the rate reaction

Question 15

How does increasing the pressure increase the rate of reaction?

Answer 15

It causes the frequency of collisions to increase and so increases the rate of reaction. There are more particles in the same volume of water.

Question 16

What is a catalyst?

Answer 16

A catalyst speeds up the rate of reaction but is not used up itself during the reaction. It remains chemically unchanged. It increases the rate of reaction by reducing the activation energy of the substance

Question 17

Is there one catalyst for all reactions?

Answer 17

No, Different catalysts are needed for different reactions

Question 18

Catalysts in industry.

Answer 18

Catalysts are used whenever possible in industry to increase rates of reaction and reduce energy costs.

Question 19

What is a reversible reaction?

Answer 19

In a reversible reaction, the products of the reaction can react to make the original reactants.

Question 20

Give an example of a reversible reaction.

Answer 20

Heating ammonium chloride into gas will condense back into ammonium chloride

Question 21

What are the 4 things that can affect the rate of reaction?

Answer 21

Temperature
Pressure/concentration
Surface area
Catalyst

Question 21

What is a reversible reaction/ describe a reversible reaction.

Answer 21

A reversible reaction can go backwards.
e.g. A+B = C+D
A + B is reacting to form C + D
At the same time C + D is reacting to form A + B

Question 22

What is equilibrium in a reversible reaction?

Answer 22

After a while of the reversible reaction happening the forward and backwards reaction will be happening at the same rate, this is when the system can be described as being in equilibrium.

Question 23

What does it mean for the reaction when it is in equilibrium?

Answer 23

The forward and backwards reaction will be happening at the same time. Both reactions are still happening but there is no overall effect, it means the concentrations of the reactions have reached a balance and wont change

Question 24

What is a closed system?

Answer 24

A closed system is a system in which none of the reactants can escape the container and nothing can get into the container. It is only in a closed system that equilibrium can happen.

Question 25

If an equilibrium lies to the right what does it mean?

Answer 25

The concentration of products is greater than that of the reactants

Question 26

If the equilibrium lies to the left what does it mean?

Answer 26

The concentration of reactants is greater than that of the products

Question 27

What conditions affect the position of equilibrium?

Answer 27

Temperature
Pressure (only in gasses)
Concentration

Question 28

Describe exo and endothermic reactions in a reversible reaction

Answer 28

In a reversible reaction , if the reaction is endothermic in one direction the reaction will be exothermic in the other.
e,g. Heating blue hydrated copper is a endothermic reaction
Adding water back to the copper which was dehydrated is an exothermic reaction

Question 29

What is La Chateliers principle?

Answer 29

The idea that if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract the change

Question 30

How does the condition in a reversible reaction at equilibrium respond to a change in temperature?

Answer 30

If you DECREASE the temp the equilibrium will move in the exothermic direction to produce more heat, it means you will get more products for the exothermic side of the reaction and fewer for the endothermic side of the reaction.
If you INCREASE the temp the equilibrium will move in the endothermic direction to try and reserve it. You will get more products for the endothermic reaction and fewer products for the exothermic reaction

Question 31

How does the condition in a reversible reaction at equilibrium respond to a change in pressure? (only in gasses)

Answer 31

If you increase the pressure, the equilibrium tries to reduce it, it moves in the direction with fewer molecules of gas.
If you decrease the pressure, the equilibrium tries to increase it, it moves in the direction where there are more molecules of gas.
Use a balanced symbol equation to see which side has more molecules.

Question 32

How does the condition in a reversible reaction at equilibrium respond to a change in concentration?

Answer 32

If you change the concentration of the substances the system will no longer be in equilibrium. So the system responds to brings itself back to equilibrium.
If you increase the concentration of the reactants the system tries to decrease it by making more products
If you decrease the concentration the products in the system tries to increase it by reducing the amount of reactants