Question

In Quantitative Analysis, when and why do we need to consider activities?

Answer 1

In Quantitative Analysis, we need to consider activities when we have to test a substance or mixture to determine the amounts and proportions of its chemical constituents. Activities are required, when we are doing gravimetric and volumetric analysis. For example in Gravimetric analysis, we determine the amount of material present by weighing the sample before and after some transformation. A common example is the determination of the amount of water in a hydrate by heating the sample to remove the water such that the difference in weight is due to the loss of water.