Rate and extent of chemical change

Question 1

What is an example of a slow reaction?

Answer 1

Chemical weathering

Question 2

What is an example of a moderate speed reaction?

Answer 2

Magnesium reacting with acid

Question 3

What is an example of a fast reaction?

Answer 3

Burning

Question 4

How do you interpret a rate of reaction graph?

Answer 4

The steeper the line, the faster the rate of reaction and the reaction becomes less steep as the reactants are used up

Question 5

What is collision theory?

Answer 5

Particles have to have enough energy for the collision to be successful and the more they collide, the more likely it is to be successful

Question 6

What is the activation energy?

Answer 6

The minimum amount of energy required in a reaction to break the bonds of the reactants, starting the reaction

Question 7

What does the rate of reaction depend on?

Answer 7

Temperature, concentration/pressure, surface area and catalysts

Question 8

What are the optimum conditions for rate and why?

Answer 8

High temperature as the particles have more energy so can move faster, higher pressure/conc as collisions are more frequent, bigger surface area as collisions are more frequent as more space to work on with same no of particles and using a catalyst as it lowers activation energy

Question 9

How do you work out rate of reaction?

Answer 9

Amount of reactant used or amount of product formed / time

Question 10

How do you measure the rate of a reaction?

Answer 10

Visual change through colour or precipitate change, change in mass to see gas given ff and the volume of gas given off

Question 11

How do you find the mean reaction rate from a graph?

Answer 11

Work out overall change in the y-value and divide this by the total time for the while reaction

Question 12

How do you find the reaction rate at a particular point on a graph?

Answer 12

Draw a tangent at that point and then work out the gradient

Question 13

How do you do the magnesium and HCl reaction experiment?

Answer 13

Place flask on scale, add HCl, set scale to 0, add magnesium ribbon, plug flask with cotton wool, start stopwatch, record mass at regular intervals

Question 14

How do you do the disappearing cross experiment?

Answer 14

Add dilute sodium thiosulfate to a flask, put flask on top of cross, ad HCl to flask, start stopwatch, record the time when the cross became unseeable

Question 15

What is an equilibrium?

Answer 15

A reversible reaction where the forward reaction is going at exactly the same time as the backwards reaction

Question 16

What happens if the equilibrium lies to the right?

Answer 16

The conc of products is greater than the reactants

Question 17

What happens if the equilibrium lies to the left?

Answer 17

The conc of the reactants is greater than the products

Question 18

What does the position of the equilibrium depend on?

Answer 18

Temperature, pressure and conc

Question 19

What is an endothermic reaction?

Answer 19

Where energy is transferred from the surroundings

Question 20

What is an exothermic reaction?

Answer 20

Where energy is transferred to the surroundings

Question 21

What is Le Chatelier’s Principle?

Answer 21

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

Question 22

What happens if you raise the temperature in an equilibrium?

Answer 22

The equilibrium will move in the endothermic direction to try and decrease it, meaning that you will now get more products for the endothermic reaction and fewer products for the exothermic reaction

Question 23

What happens if you raise the pressure in an equilibrium?

Answer 23

The equilibrium will try to reduce the pressure and move in the direction where there are more molecules of gas

Question 24

What happens if you raise the concentration?

Answer 24

The reactants of the system try and decrease it by making more products