2: Atoms and reactions : titrations

Question 1

What is a standard solution and how is one formed?

Answer 1

A standard solution is a solution of known concentration.

1. dissolve an accurately weighed mass of solid in a known volume of solvent using a volumetric flask
2. fill up to the line with water for optimum accuracy
3. use standard solution to find the concentration of another solution with an unknown concentration

Question 2

What is a titration used for?

Answer 2

A titration is used to identify the concentration of a solution by reacting it with a solution of known concentration and measuring the volume required for a complete reaction.

Question 3

Why does the pipette first need to be rinsed with distilled water and then with the alkali?

Answer 3

• with water to remove any unwanted chemicals
• with alkali to remove any water droplets which could dilute the solution

Question 4

Why does the pipette need to be filled with the alkali just past the 25cm cubed mark?

Answer 4

The level of the liquid will drop slightly when the pipette is lifted out of the alkali

Question 5

Why should only a few drops of indicator be added?

Answer 5

Indicators are weak acids so adding too much could give inaccurate results

Question 6

Why does the conical flask need to be swirled as the acid is being added?

Answer 6

To ensure that the acid and alkali mix thoroughly so they can react.