Practicals

Question 1

Describe a method to make pure, dry crystals of magnesium sulfate from a metal oxide and a dilute acid

Answer 1

1. Add sulfuric acid to a beaker
2. Warm sulfuric acid
3. Add metal oxide and stir
4. Continue adding metal oxide until it is in excess
5. Filter out excess metal oxide using filter paper and a funnel
6. Heat solution in an evaporating basin to crystallisation point
7. Leave in a cool place to crystallise
8. Pat dry with filter paper

Question 2

Plan an experiment to investigate temperature change

Answer 2

1. Place a polystyrene cup in a beaker
2. Use a measuring cylinder to put 25cm³ of dilute hydrochloric acid into the cup
3. Place a lid on the cup and make a hole in it
4. Place the thermometer into the hole and record the starting temperature
5. Use the measuring cylinder to put 5cm³ of sodium hydroxide into the cup
6. Swirl the solution using the thermometer
7. Record the highest temperature reached
8. Repeat experiment several times, increasing volume of sodium hydroxide by 5cm³ each time until it reaches 40cm³

Question 3

Give one independent variable in the temperature change experiment

Answer 3

Volume of sodium hydroxide solution

Question 4

Give one control variable in the temperature change experiment

Answer 4

Volume of hydrochloric acid

Question 5

Give one dependent variable in the temperature change experiment

Answer 5

Temperature change

Question 6

Plan an experiment to investigate how the concentration of a reactant affects the rate of reaction (disappearing cross experiment)

Answer 6

1. Use a measuring cylinder to put 10 cm³ of sodium thiosulfate into a conical flask
2. Place the conical flask onto a printed black cross
3. Add 10cm³ of hydrochloric acid to the conical flask
4. Swirl solution and start a stopwatch
5. Look down through the top of the flask
6. Stop the clock when the cross can no longer be seen
7. Repeat experiment using different concentrations of sodium thiosulfate

Question 7

Plan an experiment to investigate how the concentration of a reactant affects the rate of reaction (volume of gas released)

Answer 7

1. Use a measuring cylinder to put 50cm³ of hydrochloric acid into a conical flask
2. Connect the bung and delivery tube to the flask
3. Connect the tube to the gas syringe/upside down measuring cylinder
4. Add a 3cm piece of magnesium ribbon to the flask
5. Start a stopwatch
6. Record the volume of hydrogen gas collected every 10 seconds
7. Continue until no more hydrogen is given off
8. Repeat experiment with different concentrations of hydrochloric acid

Question 8

Write a method for chromatography

Answer 8

1. Draw pencil start line on chromatography paper
2. Place spot of [mixture] on start line
3. Place [solvent] in a beaker
4. Place chromatography paper in solvent
   –> [solvent] should be below start line
5. Use a lid
6. Wait for solvent to travel up chromatography paper
7. Mark solvent front
8. Dry the chromatography paper

Question 9

Write a method for a flame test

Answer 9

1. Clean wire (using HCl)
2. Dip wire into unknown compound
3. Place in roaring (blue) flame
4. Observe the colour

Question 10

Name the 5 metal compounds that can be detected through flame tests

Answer 10

• Lithium
• Sodium
• Potassium
• Calcium
• Copper
  (LSPCC)

Question 11

Name the colour produced from a positive lithium flame test

Answer 11

Crimson

Question 12

Name the colour produced from a positive sodium flame test

Answer 12

Yellow

Question 13

Name the colour produced from a positive potassium flame test

Answer 13

Lilac

Question 14

Name the colour produced from a positive calcium flame test

Answer 14

Orange-red

Question 15

Name the colour produced from a positive copper flame test

Answer 15

Green

Question 16

Write a method to test for carbonate ions, including the positive result

Answer 16

1. Put carbonate into a test tube
2. Add dilute hydrochloric acid
3. Bubble through limewater
   —> Limewater turns cloudy

Question 17

Give the positive result for a carbonate ion test

Answer 17

Limewater turns cloudy

Question 18

Write a method to test for halide ions

Answer 18

1. Add halide to test tube
2. Add nitric acid
3. Add silver nitrate solution

Question 19

Give the result for a positive chloride test

Answer 19

White precipitate

Question 20

Give the result for a positive bromide test

Answer 20

Cream precipitate

Question 21

Give the result for a positive iodide test

Answer 21

Yellow precipitate

Question 22

Outline the purpose of chromatography

Answer 22

Separate mixtures into their components and identify them

Question 23

Name the two phases in chromatography

Answer 23

• Stationary phase
• Mobile phase

Question 24

Identify the mobile phase in chromatography

Answer 24

The solvent

Question 25

Identify the stationary phase in chromatography

Answer 25

The chromatography paper

Question 26

Describe the relationship between the solubility of a substance and how far it moves up the paper in chromatography

Answer 26

The more soluble the substance, the further up the paper it moves (and vice versa)

Question 27

Name the value that is used to identify substances in chromatography

Answer 27

Rf value

Question 28

Give the equation used to calculate the Rf value of a substance

Answer 28

distance travelled by substance/distance travelled by solvent

Question 29

Outline the difference between the appearance of a mixture and a pure substance on chromatography paper

Answer 29

- Mixture will produce multiple spots - Pure substance will only produce one spot

Question 30

State why mixtures of ions are difficult to detect using flame tests

Answer 30

Some colours can be masked by others

Question 31

Write method to test for sulfate ions, including the positive result

Answer 31

1. Add sulfate to test tube 2. Add dilute hydrochloric acid 3. Add barium chloride ---> White precipitate will form

Question 32

Name the white precipate formed in a positive sulfate ion test

Answer 32

Barium sulfate

Question 33

Write the word equation for the reaction of magnesium sulfate with barium chloride

Answer 33

magnesium sulfate + barium chloride --> barium sulfate + magnesium chloride

Question 34

Name the three precipitates that can form from a positive halide ion test

Answer 34

- Silver chloride - Silver bromide - Silver iodide

Question 35

Identify the 3 stages of the water purification practical

Answer 35

- pH test - Crystallisation - Distillation

Question 36

Explain why a pH test is done in the water purification practical

Answer 36

Pure water has a pH of 7 --> pH that is not 7 shows the water contains dissolved acid/alkali

Question 37

Write the method to test for dissolved solids in the water purification practical

Answer 37

1. Weigh an empty evaporating basin using a mass balance 2. Fill the basin with the water sample 3. Place basin on tripod and gauze 4. Heat basin with bunsen burner until water evaporates 5. Wait for evaporating basin to cool 6. Weigh evaporating basin again

Question 38

Describe the result in the water purification practical if there are dissolved solids inside the water

Answer 38

The mass of the evaporating basin will increase

Question 39

Write a method to purify the water through distillation in the water purification practical

Answer 39

1. Set up tripod and gauze with bunsen burner underneath 2. Place conical flask with water sample on top with bung and deliver tube attatched 3. Place the delivery tube into a test tube 4. Place the test tube into a beaker of ice water 5. Heat water sample until it evaporates 6. Wait until water collects in the test tube in the beaker