Iodine-Thiosulfate Titrations

What is the main purpose of an iodine-thiosulfate titration?

• To determine the concentration of an oxidising agent

• To neutralise an acid

• To find the solubility of iodine

• To identify a base

What type of reaction occurs in an iodine-thiosulfate titration?

• Neutralisation

• Precipitation

• Redox

• Hydration

In this titration, iodine acts as the:

• Oxidising agent

• Reducing agent

• Base

• Indicator

In this titration, thiosulfate ions act as the:

• Reducing agent

• Oxidising agent

• Catalyst

• Acid

Why is iodine not used as a primary standard?

• It is too reactive

• It is only slightly soluble in water and volatile

• It has an undefined formula

• It is difficult to weigh accurately due to low density

Which solution is used to generate iodine for the titration?

• Hydrochloric acid

• Sulfuric acid

• Nitric acid

• Acetic acid

Why is potassium iodate used in the standardisation step?

• It acts as an indicator

• It is volatile

• It is a primary standard and can be used to produce a known amount of iodine

• It reacts with sodium thiosulfate directly

What is the colour of the iodine solution before any thiosulfate is added?

• Brown

• Blue-black

• Colourless

• Yellow

What happens to the colour of the iodine solution as thiosulfate is added?

• It becomes darker

• It fades from brown to pale yellow

• It turns blue

• It stays brown

Why is starch not added at the start of the titration?

• It acts too slowly

• It would make the solution too acidic

• It forms a stable complex with high concentrations of iodine and would give a permanent blue colour

• It would react with thiosulfate directly