Core practicals: paper 1

Question 1

What is chromatography used for?

Answer 1

To separate a soluble substance

Question 2

What is the solvent and solute in chromatography?

Answer 2

solvent: water
solute: ink spots

Question 3

HOw do you calculate the Rf value of a chromatogram?

Answer 3

distance moved by spot/distance moved by solvent

Question 4

Out line the method behind measuring the pH change when an acid is neutralised.

Answer 4

• An acid is poured into a beaker
• Add a mass of base like calcium hydroxide
• keep adding that mass and check pH change on a pH probe

Question 5

What does the trend look like for the acid neutralisation practical?

Answer 5

When the first masses of base like calcium hydroxide is added, there will be small changes in pH. Then it will suddenly increase in pH and neutralise. Then will go back to slowly increase in pH every time a mass is added.

The graph would look like a stretched S shape (wont go down in pH)

Question 6

What general equations can be useful for the dry salts practical?

Answer 6

acid + base = salt + water
acid + hydroxide = salt + water
acid + carbonate = salt + CO2 + water
acid + metal = salt + hydrogen

Question 7

How is a titration performed?

Answer 7

1) A burette is filled with an acid
2) Fill a conical glass with an alkali
3) add a few drops of an indicator such as phenolphalein
4) let the acid drop into the alkali and when the purple colour changes to clear, then it has been neutralised

You can then work out how much acid has been used to do this

Question 8

How do you do you work out the concentration of the alkali?

Answer 8

E Write out the Equation, mass and concentration of known substances
M Work out the number of moles through concentrations/(volume/1000)
M equate into the molar ratio
A answer, find the concentration of the alkali through number of moles/(volume/100)

Question 9

What is the equation to work out the concentration from a titre?

Answer 9

moles/(volume/1000)

Question 10

What electrode are anions attracted to?

Answer 10

positive anode

Question 11

What electrode are cations attracted to?

Answer 11

negative cathode

Question 12

What happen in electrolysis when using copper electrodes?

Answer 12

The positive anode loses mass as the positive copper ions are attracted to the negative cathode.

Question 13

Why is the labatory method not suitable for large scale production of ammonium nitrate crystals?

Answer 13

• too large for titration

- large volumes need to be heated to form crystals using a lot of energy