p110 solutions

 

Exercises

 

1. The following table gives the colours of the indicator phenol red in solutions whose pH values vary from 0 to 14.

A few drops of this indicator are added to a basic solution.

 

What colour does the phenol red become?

Orange or red

 

2.

 

pH Scale

 

2

 

3

 

4

 

5

 

6

 

7

 

8

 

9

 

10

 

11

 

12

 

Indicator 1

 

Yellow

 

Green

 

Blue

 

Indicator 2

 

Colourless

 

Pink

 

Fuchsia

 

Indicator 3

 

Red

 

Orange

 

Yellow

 

Indicator 4

 

Red

 

Orange

 

Yellow

 

Green

 

 

You are given a solution and told it is neutral. You would like to check if this is true.

 

Which of the indicators in the table will you use? (pick only one)

 

Indicator 1; it has the narrowest turning point

 

3.

 

pH Scale

 

2

 

3

 

4

 

5

 

6

 

7

 

8

 

9

 

10

 

11

 

12

 

Indicator 1

 

Yellow

 

Green

 

Blue

 

Indicator 2

 

Colourless

 

Pink

 

Fuchsia

 

Indicator 3

 

Red

 

Orange

 

Yellow

 

Indicator 4

 

Red

 

Orange

 

Yellow

 

Green

 

 

The pH of a given solution is unknown. Indicators 1 and 3 turn yellow in this solution.

 

What colour will indicator 4 become in this solution?

 

orange

 

4. Below is the colour chart for an indicator.

 

Maria carries out the following experiment : she numbers four test tubes 1 to 4 and into each adds 2 mL of the following substances and two drops of the indicator.

 

 

EXPERIMENT

 

RESULTS

 

Test-tube

 

Substances

 

Colours

 

N 1

 

2 mL of Drano solution

 

indigo-blue

 

N 2

 

2 mL of vinegar

 

red

 

N 3

 

2 mL of soft drink

 

orange

 

N 4

 

2 mL of sodium bicarbonate solution

 

blue green

 

List the four test-tubes from least to most acidic.

 

1,4,3,2


5. The following table gives the colours of two indicators (A and B) when they are added to solutions with different pH values.

 

 

After adding a few drops of each indicator to a colourless solution of unknown pH, a student noticed that this solution turned blue.

 

What is the pH range of this solution?

 

6 to 10 ( remember: we have a mixture of the two indicators)

 

6. The following table gives the colour of a universal indicator when it is added to solutions with different pH values.

 

 

pH

 

1

 

3

 

5

 

7

 

9

 

11

 

13

 

Colour

Red

Orange

Yellow

Green

Turquoise

Blue

Purple

 

In order to determine the nature of a solution, a student added a few drops of this universal indicator to a sample of the solution. The sample turned purple.

 

Was the student a given a strong base? Explain.

 

Yes. The higher the pH, the stronger the base.

 

7. a. Give the turning points for each of the following:

 

1) Methyl orange: 3.2 to about 4.7

pH

1

2

3

4

5

6

7

8

9

10

11

12

13

14

 

Red

Orange

Yellow

 

2) Bromothymol blue: 6.3 to 7.8

pH

1

2

3

4

5

6

7

8

9

10

11

12

13

14

 

Yellow

Green

Blue

 

b. If you had a strongly acidic solution with bromothymol blue indicator, and you slowly added base, what colour changes would you see?

Yellow to green to blue.

 

c. In 7(b), suppose you had created a strongly basic solution. How would you create a green solution?

Slowly add acid.