Q9s

Question 1

Define according to Bronsted-Lowry theory an acid?

Answer 1

An acid is a proton donor or H+ donor.

Question 2

Define according to Bronsted-Lowry theory a base?

Answer 2

A base is a proton acceptor or H+ acceptor.

Question 3

Define according to Bronsted-Lowry theory an acid-base conjugate pair?

Answer 3

Two species that differ by a proton or H+.

Question 4

Distinguish between a weak acid and a strong acid?

Answer 4

A weak acid is a poor proton donor or H+ donor and is slightly dissociated. A strong acid is a good proton donor or H+ donor and is fully dissociated.

Question 5

Give an example of a weak acid?

Answer 5

Acetic acid (vinegar), ethanoic acid, phosphoric acid, citric acid, and methyl orange.

Question 6

Define a concentrated acid solution?

Answer 6

A concentrated acid solution has a large quantity of acid (solute) in a small volume of water (solvent).

Question 7

Define a dilute acid solution?

Answer 7

A dilute acid solution has a small quantity of acid (solute) in a relatively large volume of water (solvent).

Question 8

Define a concentrated base solution?

Answer 8

A concentrated base solution has a large quantity of base (solute) in a small volume of water (solvent).

Question 9

Define a dilute base solution?

Answer 9

A dilute base solution has a small quantity of base (solute) in a relatively large volume of water (solvent).

Question 10

Define Amphoteric?

Answer 10

Amphoteric is a substance that can act as an acid or a base.

Question 11

Define pH?

Answer 11

pH = -log10[H+] or pH = -log10[H30+]. It is the hydrogen ion concentration.

Question 12

Define a standard solution?

Answer 12

A standard solution is a solution of known concentration.

Question 13

Define a saturated solution?

Answer 13

A saturated solution is a solution with the maximum quantity or mass of solute dissolved at that temperature.

Question 14

Define Anhydrous?

Answer 14

Anhydrous contains no water or is dried.

Question 15

Define a primary standard?

Answer 15

A primary standard is stable, can be weighed accurately, pure, solid, and does not lose or absorb water.

Question 16

How should the pipette be prepared before use?

Answer 16

Rinse with deionised water and then with the solution it will deliver. Use a pipette filler, fill to the zero mark, release liquid, and allow time to drain.

Question 17

Why was a pipette filler used to fill the pipette?

Answer 17

For safety and to avoid swallowing.

Question 18

How should the burette be prepared before use?

Answer 18

Rinse with deionised water and then with the solution it will deliver. Fill using a funnel and remove it. Open the tap to reach the zero mark and adjust to volume at eye level.

Question 19

How should the conical flask be prepared before use?

Answer 19

Rinse with deionised water only.

Question 20

Why is a conical flask suitable for use as a titration flask?

Answer 20

Its sides can be washed down easily, allows swirling, and prevents splashing.

Question 21

Why are the sides of the conical flask washed down with deionised water?

Answer 21

To ensure all the solution reacts.

Question 22

What is the procedure for transferring exactly 25.0 mL of solution from the pipette to a conical flask?

Answer 22

Allow the pipette to drain for a few seconds and touch the tip against the wall of the titration flask.

Question 23

Why was a conical flask placed on a white tile?

Answer 23

To allow the color change/end point to be seen clearly.

Question 24

How do you read the burette?

Answer 24

Read at eye level, at the bottom of the meniscus, and use white paper to read clearly.

Question 25

How could the presence of an air bubble in the nozzle of a burette affect the result obtained in a titration reading?

Answer 25

It could cause an inaccurate reading.

Question 26

Define a volumetric flask?

Answer 26

A volumetric flask is used to make up a standard solution. It has a narrow neck for accurate measurement and can be stoppered for mixing.

Question 27

Procedure to make up a standard solution?

Answer 27

Weigh out sodium carbonate, add to a beaker with deionised water, dissolve, transfer to volumetric flask, fill to mark with deionised water, stopper and invert several times.

Question 28

Why is it important not to use tap water in the experiment?

Answer 28

Tap water contains ions or impurities, which could interfere with the result.

Question 29

Define an acid-base indicator?

Answer 29

An acid-base indicator is a substance that changes color in solutions of different pH.

Question 30

Indicator used for strong acid vs strong base titration?

Answer 30

Methyl orange (red to yellow) or phenolphthalein (colourless to pink).

Question 31

Indicator used for strong acid vs weak base titration?

Answer 31

Methyl orange (yellow to red).

Question 32

Indicator used for weak acid vs strong base titration?

Answer 32

Phenolphthalein (colourless to pink).

Question 33

Indicator used for strong base vs weak acid titration?

Answer 33

Phenolphthalein (pink to colourless).

Question 34

Why should only one or two drops of indicator be used?

Answer 34

Indicators are weak acids/bases, and too much could affect the accuracy of the result.

Question 35

Define a saturated solution?

Answer 35

A saturated solution has the maximum quantity or mass of solute dissolved at that temperature.

Question 36

Define anhydrous sodium carbonate?

Answer 36

Anhydrous sodium carbonate contains no water and is dried.

Question 37

Define a primary standard?

Answer 37

A primary standard is stable, pure, solid, and can be weighed accurately without absorbing or losing water.

Question 38

Common use of limewater in the laboratory?

Answer 38

To detect the presence of carbon dioxide gas.