Rates and Energy

Question 1

What are three ways that you could do a rate of reaction experiment?

Answer 1

• Precipitation reaction (the time it takes for a precipitate to form)
• Mass change (change in mass over time)
• Volume of gas ( given off during a time period, for a reaction)

Question 2

Rate of reaction equation?

Answer 2

amount of reactants used or amount of product formed / time

Question 3

How do you carry out the marble chip experiment?

Answer 3

1. Place marble chips in a flask with a dilute hydrochloric acid
2. Place a syringe on top of the flask and attach it to the flask, making sure that everything is air-tight.
3. Start the timer as the reaction happens and stop it at regular intervals, measuring the volume of gas captured each time.
   - Do the same experiment with the same amount of everything but this time crush the chips.

Question 4

What conclusion can you draw from the marble chips experiment? (About the surface are of a reactant)

Answer 4

The finer the chips (bigger) the sooner the reaction finished, meaning that this was the fastest reaction time.

Question 5

What other factors can increase the reaction rate in the marble chip experiment? (Most other reaction) (Other than surface area and temperature)

Answer 5

Increasing the concentration of the hydrochloric acid.

Question 6

How is sodium thiosulphate and hydrochloric acid practical performed?

Answer 6

1. Mix both mixtures into a conical flask
2. Place the conical flask on black spot
3. Measure the time it takes for a precipitate to form and cloud your vision towards the black spot. (This is the reaction time)
   - Try at different temperatures to see how that effect the reaction time.

Question 7

What factors does the rate of reaction depend on?

Answer 7

Temperature
Surface area
Concentration
Pressure (gases)

Question 8

What factors affect collisions?

Answer 8

collision frequency

Energy transferred at each collision

Question 9

What is activation energy?

What is the two meaning?

Answer 9

The minimum amount of energy particles needs when they collide, for a reaction to start.

The minimum amount of energy needed for bonds to break.

Question 10

How does increasing temperature increase reaction?

Answer 10

• Particles have more kinetic energy and thus move around more. (More collisions = more reaction)
• More energy is transferred in collisions

Question 11

How does increasing concentration (or pressure) increase reaction?

Answer 11

• More particles with a volume mean that more collisions can occur.
• In a gas increasing pressure means particles are more crowded and more collisions can occur.

Question 12

How does an increase in the surface area affect the reaction rate?

Answer 12

-Particles will have more areas to collide with and transfer energy which means that the rate of reaction will increase.

Question 13

How do catalysts work and increase the rate of reaction?

Answer 13

They provide an alternative path for a reaction that requires lower activation energy.

Question 14

What are the 4 main reactions that are exothermic?

Answer 14

salt dissolving in water
Precipitation
Displacement
Neutralisation

Question 15

Is bond-breaking Exo or endo?

Answer 15

Exothermic

Question 16

Is bond-making exo or endo?

Answer 16

Endothermic

Question 17

What does exothermic reaction mean?

Answer 17

More energy when forming bonds that breaking

Question 18

What does endothermic reaction mean?

Answer 18

More energy when breaking bonds than making