Chemical Reactions

Question 1

What does the law of conservation of mass state?

Answer 1

In a chemical reaction, no matter is destroyed or created

Question 2

What is a chemical change?

Answer 2

A rearrangement of the atoms in the reactants, to form the products

Question 3

Why may the balance reading for the products be more than the reading for the reactants?

Answer 3

Gas from the air reacted with the reactants

Question 4

What is the formula that links mass, moles, and Mr?

Answer 4

moles = mass/Mr

Question 5

What is the limiting reactant?

Answer 5

It all reacts and limits how much product can be formed

Question 6

What does it mean for a reactant to be ‘in excess’?

Answer 6

It does not all react, and has no affect on the amount of product formed

Question 7

If the reactant molecules in a reaction have more energy in their chemical bonds than the product molecules, will energy be absorbed or released overall?

Answer 7

released

Question 8

What is an exothermic reaction?

Answer 8

A reaction that releases thermal energy to the surroundings

Question 9

What is an endothermic reaction?

Answer 9

A reaction that takes in thermal energy from the surroundings

Question 10

If an exothermic reaction occurs in a closed container, what would happen to the temperature inside the container?

Answer 10

The temperature would increase

Question 11

If an endothermic reaction occurs in a closed container, what would happen to the temperature inside the container?

Answer 11

The temperature would decrease

Question 12

what is activation energy?

Answer 12

the minimum amount of energy the reactant particles require in order to collide successfully with each other and react.

Question 13

On reaction profile diagrams, what is the activation energy?

Answer 13

the increase in energy from the reactants to the peak of curve.

Question 14

Does breaking bonds release energy or require energy?

Answer 14

require

Question 15

Is breaking bonds exothermic or endothermic?

Answer 15

Endothermic

Question 16

What is bond energy?

Answer 16

the amount of energy required to break one mole of a particular bond.

Question 17

Is forming a bond an exothermic or endothermic process?

Answer 17

exothermic

Question 18

How do you calculate the overall enthalpy change of a reaction?

Answer 18

(energy of) bonds formed - (energy of) bonds broken

Question 19

What type of reaction produces a negative energy change?

Answer 19

An exothermic reaction

Question 20

What does the pH scale measure?

Answer 20

acidity or alkalinity of a solution

Question 21

What pH does stomach acid typically have?

Answer 21

about 2

Question 22

What are 2 ways to measure the pH of a solution?

Answer 22

Chemical indicator

pH probe

Question 23

What ion is responsible for making a solution alkaline when it’s dissolved in it?

Answer 23

OH -

Question 24

Which products are formed when an acid reacts with a metal oxide?

Answer 24

a salt and water

Question 25

What type of reaction is it when an acid and a base react together?

Answer 25

Neutralisation reaction

Question 26

Which products are formed when an acid reacts with a metal hydroxide?

Answer 26

a salt and water

Question 27

Which products are formed when an acid reacts with a metal carbonate?

Answer 27

a salt, water and carbon dioxide

Question 28

What does it mean when an acid ionises?

Answer 28

when the acid molecules are added to water, they split apart

Question 29

Whats the difference between a strong and a weak acid?

Answer 29

Strong acids ionise completely, whereas weak acids only partially ionise.

Question 30

What are 3 strong acids?

Answer 30

Nitric acid Sulfuric acid Hydrochloric acid

Question 31

is the ionisation of weak acids reversible?

Answer 31

yes

Question 32

What are 3 weak acids?

Answer 32

carbonic ethanoic citric

Question 33

As the concentration of hydrogen ions in a solution increases, what happens to the pH?

Answer 33

The pH decreases

Question 34

A solution decreases from pH 6 to pH 5. By what factor has the concentration of hydrogen ions increased?

Answer 34

x10

Question 35

With respect to electrons, reduction is:

Answer 35

The gain of electrons

Question 36

With respect to electrons, oxidation is:

Answer 36

the loss of electrons

Question 37

What is a spectator ion?

Answer 37

an ion that doesn't take part in the reaction and so keeps the same charge

Question 38

An electrolysis cell has two electrodes. What is the name of the positive electrode?

Answer 38

anode

Question 39

An electrolysis cell has two electrodes. What is the name of the negative electrode?

Answer 39

cathode

Question 40

What is the name of the liquid the electrodes are put in?

Answer 40

electrolyte

Question 41

In electrolysis, which direction do the electrons travel?

Answer 41

Anode ➔ Cathode

Question 42

What does the term 'inert' mean?

Answer 42

unreactive

Question 43

In the electrolysis of molten lead bromide, what is the product at the anode?

Answer 43

bromine

Question 44

In electrolysis, why does the compound you're trying to separate need to be molten or dissolved?

Answer 44

So that the ions are free to move around (and go to their respective electrode)

Question 45

Which 2 chemical processes are used to extract metals from their ores?

Answer 45

reduction with carbon and electrolysis

Question 46

What is electrolysis?

Answer 46

the splitting of an ionic compound using electricity

Question 47

Why is electrolysis not used to extract all metals?

Answer 47

Electrolysis is expensive because it requires a large amount of electricity

Question 48

When should a metal be extracted by carbon reduction?

Answer 48

When the metal is less reactive than carbon

Question 49

Why is electrolysis used to extract aluminium from its ores?

Answer 49

it is more reactive than carbon

Question 50

What is the name of the substance that is mixed with aluminium oxide to lower its melting point?

Answer 50

cryolite

Question 51

In the electrolysis of a solution, which two ions are present from the water molecules themselves?

Answer 51

H+ OH-

Question 52

What is the rule to determine which ion get discharged at the cathode in aqueous electrolysis?

Answer 52

the ions of the least reactive metal will be discharged (usually copper or hydrogen)

Question 53

What is the rule to determine which ion get discharged at the anode in aqueous electrolysis?

Answer 53

If halide is present, it gets discharged, otherwise hydroxide gets discharged

Question 54

What does OH- form once it is discharged?

Answer 54

water and oxygen gas

Question 55

What is the order of the reactivity series?

Answer 55

Potassium Sodium Lithium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Hydrogen Copper Silver Gold Platinum