Rates Of Reaction

Question 1

What can change the rate of reaction?

Answer 1

-surface area
-concentration
-temperature
- use of a catalyst

Question 2

What does the gradient tell us?

Answer 2

The rate of reaction

Question 3

What has to happen for a reaction to occur? (Collision theory)

Answer 3

-reactant particles must collide
-must collide with energy >the activation energy

Question 4

What is a catalyst?

Answer 4

• substance that speeds up the rate of reaction
• doesn’t get used up
  -remains chemically unchanged

Question 5

Explains what happens to the rate of reaction when the temperature is changed

Answer 5

The particles will gain kinetic energy (which will make them move faster) and the collision will be faster per unit time (more frequent)
-more particles collide with energy>activation energy

Question 6

What will change if you change the pressure in gases?

Answer 6

Number of particles in a given volume

Question 7

Explain what will happen to the rate of the reaction if the concentration is changed

Answer 7

Means that there are more particles of that reactant in a given volume,more collision between reactant particles per unit time

Question 8

Explain what will happen to the rate of the reaction if the surface area is changed

Answer 8

Smaller pieces have a bigger surface area, more particles of solid are in contact with other reactant

Question 9

What is the equation for calculating average rate?

Answer 9

Rate= change in amount of product/time
Rate= change in amount of reactant/time

Question 10

What is the word equation for the marble chip practical ?

Answer 10

Calcium carbonate + hydrochloric acid=
calcium chloride + carbon dioxide +water

Question 11

What is the symbol equation for the marble chip practical ?

Answer 11

CaCO3+2HCl=
CaCl2+CO2+H2O

Question 12

How does a catalyst work?

Answer 12

Provides an alternative pathway with lower activation energy
This means that more collisions will have energy equal to/greater that the activation energy, so more successful collisions

Question 13

What does collision theory states in order for a reactant to occur?

Answer 13

Reactants must collide with sufficient energy-greater than or equal to the activation energy for the reaction

Question 14

What is activation energy?

Answer 14

Minimum amount of energy particles must possess if they are to react when they collide

Question 15

What is rate of reaction measured in?

Answer 15

Number of successful collisions

Question 16

Referring to the collision theory, why the rate of reaction decreases as the reaction proceeds?

Answer 16

As time goes, reactant particles get used up as there are fewer reactant particles, there are fewer successful collisions per unit time
Less frequent collisions

Question 17

Why is increasing surface area increases the rate of reaction?

Answer 17

Smaller pieces have a bigger surface area than larger pieces with the same total mass
This means more particles of the solid reactant are in contact with particles of the other reactant
This results more collisions between reactant particles per unit time, so the rate of reaction increases

Question 18

Why is increasing concentration increases the rate of reaction?

Answer 18

Increasing concentration of a solution means that there are more particles of that reactant in a given volume
As a result there are more collision between reactant particles per unit time, so the rate of reaction increases

Question 19

Why is increasing pressure of the gaseous reactant increases the rate of reaction?

Answer 19

Increasing the pressure means that there are more reactant 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 20

Why is increasing temperature increases the rate of reaction?

Answer 20

At higher temperature, reactant particles have more kinetic energy and so move around faster. This results in more collisions per unit time
+more particles will collide with energy equal to/greater than the activation energy, so more successful collisions

Question 21

What happens to the rate of reaction when a catalyst is present?

Answer 21

Catalyst provide an alternative reaction pathway with a lower activation energy
Which means more collisions will have energy equal to/greater that the activation energy= more successful collisions