Quantitative Chemistry revision random pages 123 - 136

Question 1

What two values are needed to calculate the relative formula mass of ammononia NH3?

Answer 1

The relative atomic mass of nitrogen and the relative atomic mass of hydrogen

Question 2

What is the value of the Avogardro constant?

Answer 2

602 000 000 000 000 000 000 000

or

6.02 x 10²³ per mole

Question 3

What mass of carbon dioxide (Mr = 44) will contain one mole of carbon dioxide molecules?

Answer 3

44g

Question 4

How would you use the number of moles and Mr of a compound to calculate its mass?

Answer 4

Mass = number of moles x Mr

Question 5

Explain why the mass of the reactants in a reaction will always be the same as the mass of the products?

Answer 5

No atoms are lost or made during a reaction. This means that there are the same number and types of atoms on each side of a reaction equation. As a result, no mass is lost or gained and the mass of the reactants and the products will be the same

Question 6

How would the mass of an unsealed reaction container change if a solid metal reacted with oxygen gas from the air to form a solid metal oxide?

Answer 6

It would increase

Question 7

What do the numbers in front of chemical formulas in a balanced equation represent?

Answer 7

The number of moles of each substance that take part or are formed in the reaction

Question 8

What two pieces of information do you need to be able to work out how many moles of a reactant were used up in a reaction?

Answer 8

The mass that took part in the reaction and the relative formulas mass (Mr) of the reactant

Question 9

When working out the balanced equation for the reaction using reacting masses, what should you do if one of the numbers in an equation is not a whole number?

Answer 9

Multiply all of the numbers in the equation by the same amount so that they become whole numbers

Question 10

How can you describe a reactant that does not limit the amount of product formed?

Answer 10

It is in excess

Question 11

What will happen to the amount of product formed by a reaction if you double the amount of limiting reactant and all other reactants stay in excess?

Answer 11

It will double

Question 12

What term is used to describe the expected mass of a product in a reaction, based only on the masses of the reactants?

Answer 12

Theoretical yield/maximum theoretical amount

Question 13

What term is used to describe a solid substance that dissolves in a solvent?

Answer 13

A Solute

Question 14

What would happen to the concentration of a solution if the amoun of substance dissolved in the solvent was increased?

Answer 14

It would increase

Question 15

Ture or false? g/s are a unit of concentration. Explain your answer?

Answer 15

false

Units of concentration are always units of mass/units of volume, e.g. g/dm3

Question 16

How does the precision of a result affect its uncertanity?

Answer 16

The less precise a result is, the higher the uncertainty will be

Question 17

If a solution has a pH of 10, is it acidic or alkaline?

Answer 17

Alkaline

Question 18

State one way that you could measure the pH of a solution?

Answer 18

one from:

Add universal indicator and observe the colour change.

Put a pH probe in the solution with a pH meter attached and read the pH value

Question 19

Describe what occurs in a neutralisation reaction in terms of ions?

Answer 19

Hydrogen ions (H+) from the acid react with Hydroxide Ions (OH-) from the alkali to product water

Question 20

What term is used for an acid that only partially ionises in water?

Answer 20

Weak acid

Question 21

Give one example of a strong aci and one example of a weak acid?

Answer 21

One strong acid from:

Hydrochloric acid
Nitric acid
Sulfuric acid

One weak acid from:

Ethanoc acid
Citric acid
Carbonic acid

Question 22

What happens to the hydrogen ions concentration of a solution as the pH increases by 1 unit?

Answer 22

it decreases by a factor of 10

Question 23

What type of salt is produced in a neutralisation reaction using sulfuric acid?

Answer 23

A sulfate

Question 24

What is produced when metal carbonates react with acids?

Answer 24

A salt, water and carbon dioxide

Question 25

You can make a soluble salt by reacting an acid with a soluble base. Which reactant provides the positive ion for the salt?

Answer 25

The soluble base

Question 26

How would you product a solid salt from a salt solution?

Answer 26

Heat the solution using a water bath, bunsen burner or electric heater

When some of the water has evaporated, stop heating the solution and leave it to cool.

Crystals of salt will form. Filter them out of the solution and dry them

Question 27

Where should Litium go in this reactivity series?

Potassium
Sodium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen

Answer 27

between sodium and calcium

Question 28

Name one metal that forms positive ions more easily than calcium?

Answer 28

Any one from:

Lithium
Sodium
Potassium

Question 29

Give one way you could compare the reactivity of two metals by observing how they react with an acid?

Answer 29

Any one from:

The more reactive metal will product bubbles of hydrogen more quickly

The more reactive metal will cause a larger temperature change

Question 30

Give two examples of metals that dont react with water?

Answer 30

Any two from:

Zinc
Iron (but it will rust if oxygen is also prersent)
Copper
Gold

Question 31

Name the type of reaction that separates a metal from its oxide?

Answer 31

Reduction

Question 32

What is the difference between oxidation and reduction, in terms of oxygen?

Answer 32

Oxidation is the gain of oxygen, and reduction is the loss of oxygen

Question 33

Describe what happens when a metal oxide is reduced by carbon?

Answer 33

The oxide is reduced to the pure metal as oxygen is removed from it. Carbon is oxidised to carbon dioxide as it gains oxygen

Question 34

Can magnesium be extracted from its oxide by reduction with carbon? Explain your answer?

Answer 34

No.

Carbon can only take oxygen away from metals which are less reactive than carbon, but magnesium is more reactive than carbon.

Question 35

What is the term for a loss of electrons?

Answer 35

Oxidation

Question 36

How does this ionic equation show that copper has been reduced?

Zn(s) + Cu2+ (aq) &raquo_space;» Zn2+ (aq) + Cu(s)

Answer 36

It shows that the copper ion gains two electrons to form a copper atom

Question 37

What are spectator ions in a redox reaction?

Answer 37

Ions that don’t change in the reaction

Question 38

What term is used to describe a liquid or solution that can conduct electtricity?

Answer 38

Electrolyte

Question 39

Name the electrode that negative ions are attracted to during electrolysis?

Answer 39

Anode

Question 40

Explain why molten ionic compounds can be electrolysed but ionic solids cant?

Answer 40

Molten ionic compounds can be electrolysied because the ions can move freely and conduct electricity. Ionic solids, however, contain ions that are in fixed positions and can’t move to conduct electricity

Question 41

Why is aluminium oxide mixed with cryolite for electrolysis?

Answer 41

Aluminium Oxide has a very high melting point and this lowers it.

Question 42

Water breaks down to product which ions?

Answer 42

Hydrogen ions (H+) and hydroxide ions (OH-)