Chemical Analysis

Question 1

What is chromatography?

Answer 1

Chromatography is used to separate substances in complex mixtures.

Question 2

Describe how components can be identified using chromatography.

Answer 2

Components can be identified by the distance they have travelled or by the time it has taken to travel through the apparatus (retention time).

Question 3

How do you interpret the graphical results of a chromatography experiment

Answer 3

• On a graph, the quantity of a substance is shown on y-axis, and the retention time on the x-axis.
• Larger molecules take longer to move up, whereas smaller molecuels are more mobile.
• Polar molecules will move further if a polar solvent is used.

Question 4

What is volumetric analysis?

Answer 4

Volumetric analysis uses a solution of accurately known concentration in a reaction to determine the concentration of another.

Question 5

Use of titration experiments

Answer 5

1. Titrations are used to accurately determine the volumes of solution required to reach the end point of a chemical reaction.
2. Knowing this volume can then lead to calculating concentrations.

Question 6

What is a standard solution?

Answer 6

A solution of accurately known concentration.

Question 7

What are redox titrations?

Answer 7

Titrations based on redox reactions and used to determine the unknown concentration of a solution.

Question 8

Why are indicators not always needed to determine end-points of reactions?

Answer 8

In some titrations an indicator is not required as the solution may self-indicate (change colour itself). For example, acidified permanganate is purple but turns colourless when reduced.