Chemical Reactions

Question 1

What is a physical change?

Answer 1

A physical change is a change that does not produce any new chemical substances and is often easy to reverse.

Question 2

What is a chemical change?

Answer 2

A chemical change is a change where new chemical substances are formed, often with very different properties from the reactants.

Question 3

What indicates a chemical change has occurred?

Answer 3

Signs of a chemical change include colour changes, temperature changes, and effervescence (fizzing).

Question 4

What is effervescence?

Answer 4

Effervescence is the rapid escape of gas from a liquid in which it is dissolved, causing fizzing.

Question 5

What colour change occurs in the metal displacement reaction of silver nitrate and copper?

Answer 5

The solid changes from orange-brown to silver, and the solution changes from colourless to blue.

Question 6

State one example of a physical change.

Answer 6

Melting

Question 7

State the two types of reactions that cause a change in temperature.

Answer 7

Exothermic & Endothermic

Question 8

What has a greater surface area, magnesium ribbon or magnesium powder?

Answer 8

Magnesium powder has a greater surface area.

Question 9

What four factors affect the rate of a chemical reaction?

Answer 9

1. Concentration
2. Area
3. Temperature
4. Catalyst

Question 10

A steep gradient on a rate of reaction graph indicates ……..

Answer 10

A steep gradient on a rate of reaction graph indicates a fast rate of reaction.

Question 11

Will increasing or decreasing the temperature increase the rate of reaction?

Answer 11

Increasing the temperature will increase the rate of reaction.

Question 12

Define the term collision theory.

Answer 12

A theory that explains how rates of reaction depend on the frequency and energy of collisions between reactant particles.

Question 13

State the relationship between the number of collisions and the number of particles

Answer 13

The number of collisions is proportional to the number of particles present.

Question 14

Define the term successful collision

Answer 14

A successful collision is a collision between reactant particles that leads to the formation of product molecules.

Question 15

Define activation energy

Answer 15

Activation energy is the minimum energy that reacting particles must have for a reaction to occur.

Question 16

How does the increasing the kinetic energy of the particles affect the number of successful collisions?

Answer 16

Greater kinetic energy means a greater proportion of collisions will have an energy that exceeds the activation energy.

Question 17

What is a catalyst?

Answer 17

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the reaction.

Question 18

How is the rate of reaction measured?

Answer 18

Product formed or Reactant Used / Time

Question 19

Give three techniques used in a lab that are used to measure the rate of a reaction.

Answer 19

measuring mass loss on a balance.

measuring the volume of a gas produced.

measuring a reaction where there is a colour change at the end of the reaction.

Question 20

Define the term reversible reaction.

Answer 20

A reversible reaction is a reaction that can occur in both directions

Question 21

How are reversible reactions represented in chemical equations?

Answer 21

⇌

Question 22

When ammonium chloride is heated, what are the products of the reaction?

Answer 22

When ammonium chloride is heated, ammonia and hydrogen chloride are formed.

Question 23

State what is observed when hydrated copper sulfate is heated.

Answer 23

When hydrated copper sulfate is heated the colour change is blue to white and colourless liquid (water) collects at the top of the test tube.

Question 24

What is an anhydrous salt?

Answer 24

Anhydrous salts are those that have lost their water of crystallisation.

Question 25

What is the effect of decreasing the concentration of a product?

Answer 25

Decreasing the concentration of a product shifts the equilibrium to the left, favouring the reactants.

Question 26

If the concentration of a reactant decreases, how does the equilibrium shift?

Answer 26

Equilibrium shifts to the left to reduce the effect of a decrease in reactant (or an increase in the concentration of product).

Question 27

Define the term dynamic equilibrium.

Answer 27

Dynamic equilibrium is where the rate of the forward reaction equals the rate of the reverse reaction, and the concentrations of reactants and products remain constant.

Question 28

Define the term closed system.

Answer 28

A closed system is a system where none of the reactants or products can enter or leave the reaction vessel.

Question 29

Define the term open system

Answer 29

An open system is a system where the reactants or products can both enter or leave the reaction vessel.

Question 30

What is the Haber Process?

Answer 30

The Haber Process is the industrial process for manufacturing ammonia from nitrogen and hydrogen gases.

Question 31

What catalyst is used in the Haber Process?

Answer 31

The catalyst used in the Haber Process is iron.

Question 32

What is the main product of the Contact process?

Answer 32

The main product of the Contact process is sulfuric acid.

Question 33

What is the catalyst used in the main stage of the Contact process?

Answer 33

The catalyst used in the main stage of the Contact process is vanadium(V) oxide, V₂O₅.

Question 34

Define oxidation in terms of oxygen.

Answer 34

Oxidation is any reaction in which a substance gains oxygen.

Question 35

Define reduction in terms of oxygen.

Answer 35

Reduction is a reaction in which a substance loses oxygen.

Question 36

Define the term redox reaction.

Answer 36

A redox reaction is when oxidation and reduction take place simultaneously.

Question 37

What does the Roman numeral in iron(III) oxide tell us?

Answer 37

The roman numeral tells us the oxidation number of the iron.

Question 38

What is the charge of copper in copper(II) chloride?

Answer 38

The copper has a 2+ charge in copper(II) chloride.

Question 39

Define oxidation in terms of electrons.

Answer 39

Oxidation is the loss of electrons.

Question 40

Define reduction in terms of electrons.

Answer 40

Reduction is the gain of electrons.

Question 41

Define the term oxidising agent in terms of electrons

Answer 41

In terms of electrons, an oxidising agent accepts electrons. An oxidising agent is reduced.