term 2 acids and alkalis

Question 1

What is the method of the extraction of red cabbage indicator?

Answer 1

1. Tear the red cabbage leaf into small pieces.
2. Put the red cabbage into the mortar with a little sand. Grind the cabbage with the pestle.
3. Put the red cabbage into a beaker and about 100cm3 of water and heat.
4. Filter the mixture and collect the filtrate. Save this for testing.

5.Put a small amount of sample in a clean test tube. Add a few drops of the red cabbage indicator.

6.Repeat the test using the other samples.

Question 2

What colour are these chemicals in red cabbage indicator?

Sodium hydroxide
NaOH

Ammonia
NH3

Tap water
H2O

Ethanoic acid
CH3COOH

Hydrochloric acid
HCI

Sodium carbonate
Na2CO3

Answer 2

-yellow
-green
-blue/purple
-pinkish red
-red
-green

Question 3

Why is sand crushed with the red cabbage?

Answer 3

To break the cell wall of the cabbage to extract the pigment (natural indicator)

Question 4

What is meant by extraction?

Answer 4

to take the indicator out of the plant cells

Question 5

Why was the crushed cabbage heated with water?

Answer 5

the indicator is soluble in water and dissolves better in hot water

Question 6

What is the method used to separate the leaves from the solution of the red cabbage indicator?

Answer 6

Filtration

Question 7

What are the apparatus used to make red cabbage indicator?

Answer 7

mortar, pestle, filter paper, filter funnel, beaker, tripod, Bunsen burner, gauze, conical flask

Question 8

What colour would you expect the red cabbage indicator to
become in aqueous potassium hydroxide which has a pH of 13?

Answer 8

yellow/green

Question 9

What colour would you expect the red cabbage indicator to become in
aqueous nitric acid which has a pH of 1?

Answer 9

red

Question 10

If a solution turned the red cabbage indicator yellow, what effect would it have on Universal Indicator?

Answer 10

it would turn purple

Question 11

What is the pH scale for red cabbage indicator?

Answer 11

pH 1= orange
pH 2/3= pink
pH 4-6=purple
pH 7-9= blue
pH 10/11= turquoise
pH 12/13= green
pH 14= yellow

Question 12

What is the method of reacting an Acid and an Alkali to Show neutralisation?

Answer 12

1. Place 20 cm3 of ethanoic acid in a beaker and add 10 drops of universal indicator. Note down the colour and pH.
2. Add 5 cm3 of sodium carbonate solution. Stir until the bubbling stops. Note the colour of the indicator and the pH.
3. Repeat step 2, adding 5 cm3 portions until a total of 40 cm3 of the sodium carbonate has been added.

Question 13

Is neutralisation a physical or chemical change?

Answer 13

it’s a chemical change