Question

What is 'gravimetric analysis'? (Explain + Example)

Answer 1

Gravimetric analysis is when you WEIGH.

Explanation:

You take a sample and weigh it very precisely (down to one-tenth of a milligram). Then you have it undergo reactions, mainly precipitations, and weigh the result. This will e.g. tell you how much of a certain compound was in the sample.

Example (simple):
To ascertain the salt content of sea water, you measure (or weigh) an exact amount of it (say 100.00 mL). You then let the water evaporate and weigh the salt left. This will give you the w/v or w/w percentage of salts.

Example (bit more intricate):
You want to know the amount of sulfates in tap water. You take a fixed amount (say 1 L) and let it react with barium chloride. Barium sulfate will precipitate, but also barium carbonate. The latter can be dissolved from the precipitate with some hydrochloric acid. After you filter off the barium sulfate, you dry and then burn the (ash-free) filter paper, and after cooling you weigh the barium sulfate. A bit (!) of calculating will get you the amount of sulfates in the water.

Note:
Gravimetric analysis means a lot of very precise weighing, calculating. It's not used very much anymore.