CHEMISTRY - C6, rate and extent of a chemical change

Question 1

Have a look in the book at the rate of reaction graphs and their different features.

Answer 1

//

Question 2

What is the equation for the rate of a reaction?

Answer 2

Quantity of product formed (cm3)/ Time taken (s)
or
Quantity of reactant used up

Question 3

What are some of the methods for measuring the rate of the reaction?

Answer 3

1. Measure volume of gas over time, using a gas syringe or measuring cylinder to collect the gas.
2. Measure the mass change over time, we measure total mass of reaction mixture at the start and record mass at set intervals of time
3. Disappearing cross, mix reactants together and place a black cross under the reaction vessel. Time how long until the cross disappears.

Question 4

What is collision theory?

Answer 4

For a reaction to occur, the reactant particles must collide with enough energy.

Question 5

What happens to the rate of reaction if there are more successful collisions in a certain time?

Answer 5

The rate of reaction is faster/increases

Question 6

What is a catalyst?

Answer 6

A substance that speeds up chemical reactions, it provides different reaction pathway that needs a lower activation energy.

Question 7

What is equilibrium?

Answer 7

The point in a reversible reaction where the rate of the forward reaction is the same as the rate of the backward reaction.

Question 8

What factors can affect the position of dynamic equilibrium in a closed system?

Answer 8

Concentration
Pressure
Temperature

Question 9

What is activation energy?

Answer 9

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

Question 10

What are the steps for the practical measuring the production of gas?

Answer 10

1. Support a gas syringe with a stand, boss and clamp.
2. Using a measuring cylinder, add 50 cm3 of dilute hydrochloric acid to a conical flask.
3. Add 0.4 g of calcium carbonate to the flask. 5. 4. Immediately connect the gas syringe and start a stop clock.
4. Every 10 seconds, record the volume of gas produced.
5. When the reaction is complete, clean the apparatus as directed by a teacher.
6. Repeat steps 1 to 5 with different concentrations of hydrochloric acid.

Question 11

Practical - the rate of reaction by colour change.

Answer 11

1. Using a measuring cylinder, add 50 cm3 of dilute sodium thiosulfate solution to a conical flask.
2. Place the conical flask on a piece of paper with a black cross drawn on it.
3. Using a different measuring cylinder, add 10 cm3 of dilute hydrochloric acid to the conical flask. Immediately swirl the flask to mix its contents, and start a stop clock.
4. Look down through the reaction mixture. When the cross can no longer be seen, record the time on the stop clock.
5. Measure and record the temperature of the reaction mixture, and clean the apparatus as directed by a teacher.
6. Repeat steps 1 to 5 with different starting temperatures of sodium thiosulfate solution.

Question 12

What is meant by the rate of reaction?

Answer 12

The rate of a reaction is a measure of how quickly a reactant is used up, or a product is formed.

Question 13

What’s it called when a collision between particles produces a reaction?

Answer 13

A successful collision

Question 14

What two things have to happen for a reaction to take place?

Answer 14

reactant particles:
must collide with each other
the particles must have enough energy for them to react