Titrations

Question 1

What is an acid-base titration?

Answer 1

An acid-base titration is an experiment in which an acid solution is carefully added to a basic solution, or vice versa, until the reactants just neutralise each other.

Question 2

Why is an indicator used?

Answer 2

An indicator denotes the point at which the acid/base are neutralised

Question 3

What is a standard solution?

Answer 3

A standard solution is one whose concentration is known accurately. They are often used in titrations to find the concentration of another solution.

Question 4

Describe the method used for a titration

Answer 4

• Burette set up containing standard solution.
• Initial volume noted.
• Accurate known volume of other solution is added to a flask, using volumetric pipette.
• Small amount of indicator added to flask.
• Standard solution slowly added to flask.
• Flask stirred gently to ensure mixing.
• Stop adding when indicator just changes permanently.
• Final volume noted.

Question 5

Where is volume noted from in burette?

Answer 5

Bottom of meniscus.
Read to 2 d.p.

Question 6

Why is white tile used underneath flask in titration?

Answer 6

To ensure colour change shows up.

Question 7

What colour is methyl orange indicator in acid?

Answer 7

Red

Question 8

What colour is methyl orange indicator in base?

Answer 8

Yellow

Question 9

What colour is bromothymol indicator in acid?

Answer 9

Yellow

Question 10

What colour is bromothymol indicator in base?

Answer 10

Blue

Question 11

What colour is phenophthalein indicator in acid?

Answer 11

Colourless

Question 12

What colour is phenophthalein indicator in base?

Answer 12

Pink

Question 13

What is the colour at neutralisation (end point colour) of methyl orange indicator?

Answer 13

Orange

Question 14

What is the colour at neutralisation (end point colour) of bromothymol blue indicator?

Answer 14

Green

Question 15

What is the colour at neutralisation (end point colour) of phenophthalein indicator?

Answer 15

Pale pink (if base is added to acid)

Question 16

Why does rinsing the sides of the flask during a titration not affect the final volume required (the titre) (2)

Answer 16

Titre is proportional to the amount, in mol, of reactant in the flask.
Rinsing changes the concentration but not the amount of reactant in the flask.

Question 17

What is the end/equivalence point in titrations?

Answer 17

The end point or equivalence point occurs when the two solutions have reacted completely and is shown with the use of an indicator.

Question 18

Define the term concentration of a solution

Answer 18

The concentration of a solution is the amount of solute dissolved in a solvent to make 1 dm3 of solution