C5

Question 1

What is a mole as a number?

Answer 1

6x10 to the power of 23

Question 2

What is the molar mass of a substance. Use water as an example

Answer 2

It’s relative formula mass in grams. For example water is 18 (16 for oxygen and 2 for the 2 hydrogen atoms). It’s molar mass is 18g/mol

Question 3

How do you work out the empirical formulae for a compound? And what is the empirical formulae of butane? C4H10

Answer 3

Give it’s molecular formula in its simplest form

-C2H5

Question 4

What are the sodium ions in salt needed for?

Answer 4

Transmitting nerve impulses and muscle contraction

Question 5

Why are burettes normally filled with acid and not alkalis?

Answer 5

Because strong alkalis can damage glass

Question 6

What can the changes of pH in an experiment be measured by?

Answer 6

• a pH meter

- a suitable indicator

Question 7

What are single indicators?

Answer 7

Indicators containing a single substances. Which gives a sudden change in colour at the end point (tells only whether it is acid or alkali, not how strong)

Question 8

Universal indicator is a mixed indicator. What re mixed indicators?

Answer 8

A indicator that contains several different indicator, and therefore changes colour over a range of pH values.

Question 9

What is a titration?

Answer 9

A method of finding out the concentration of a acid or alkali using. Neutralisation reaction

Question 10

How do you find out a pH curve (describe the method of the experiment used)

Answer 10

1. Fill a burette full of acid
2. Measure the alkali using a pipette and fill it using a pipette filler. Then pour the alkali into a conical flask
3. Slowly pour the acid from the burette into the conical flask full of alkali.

Question 11

How is a titration carried out?

Answer 11

The same as a pH curve but they use a single indicator instead of a pH meter

Question 12

What is the titre?

Answer 12

Te volume of acid needed to exactly neutralise the alkali

Question 13

Describe how to measure has using a gas syringe

Answer 13

The glass gas syringe is connected to the container that holds the reaction in by a tube. As the reaction takes place be tube fills up and eventually the tube is pushed out.

Question 14

Describe a to carry out a upward displacement experiment.

Answer 14

You fill a measuring cylinder up with water and then turn it upside down in a trough full of water. The High air pressure keeps the water inside the container. As the reaction occurs the gas pushes the water out of the measuring cylinder

Question 15

What is equilibrium?

Answer 15

A point in a reversible reaction in which a forward reaction and a backwards reaction are occurring at the same rate

Question 16

What does rtp stand for?

Answer 16

Room temperature and pressure

Question 17

One mole of any gas occupies the same volume at rtp. What is this molar volume?

Answer 17

24dm cubed

Question 18

What are the main uses of sulphuric acid?

Answer 18

• phosphate fertilisers
• making chemicals
• making paper
• making polymers
• oil refining

Question 19

What process is used to make sulphuric acid?

Answer 19

The contact process

Question 20

What are the 3 raw materials needed for the contact process?

Answer 20

• sulfur
• air
• water

Question 21

What is the 3 step process of the contact process

Answer 21

1. Sulfur reacted with oxygen to make sulfur dioxide
2. Sulfur dioxide reacted with oxygen to form sulfur trioxide
3. Sulfur trioxide reacted with water to form sulfuric acid

Question 22

The second stage of the contact process is a reversible reaction. What are the conditions used and why?

Answer 22

• 450°c : it is an exoteric reaction so a higher yield can be obtained by reducing the temperature, however the rate of reaction will be too low if the temperature is too low
• vanadium oxide : as a catalyst to speed up the reaction
• an atmospheric pressure - it provides a good yield while not being too expensive.

Question 23

What acid does vinegar contain?

Answer 23

Ethanoic acid

Question 24

What is the concentration of a acid on terms of moles?

Answer 24

The measure of moles of acid in 1dmcubed

Question 25

What is the difference between strong and weak acids in terms of ionising?

Answer 25

Stronger acids completely ionise in water whereas weak acids only partially ionise in water. So the concentration of hydrogen ions is higher in stringer acids.

Question 26

Why is hydrogen gas always formed at the negative electrode in electrolysis?

Answer 26

Because the positive hydrogen ions are attracted to the negative electrode

Question 27

Why are weaker acids not as good at conduction electricity as stronger acids?

Answer 27

Because there are less hydrogen ions for the current to pass through

Question 28

Limescale, over time, builds up on things like washing machines, irons and kettles. But what is Limescale am what does it do to the appliances?

Answer 28

It is a deposit of calcium carbonate and makes the appliances less efficient, wasting electricity

Question 29

Why is weak acid used to remove Limescale and not strong acid?

Answer 29

Weak acid reacts with the Limescale without damaging the metal. Strong acid would damage the metal.