first and most natural way: to weigh the pellet.Of course, it must first be extracted from the solution and dried.This is done by filtration.You can use plain glass funnel with a paper filter.If you want to quickly filter out sediment, and achieve a more complete extraction of the solution it is better to use a Buchner funnel.
After the precipitate is separated from the liquid, it must be thoroughly dried (using a Buchner funnel, and the precipitate obtained is already sufficiently dry, so the drying process will take some time), and weigh.Of course, the more accurate the scales we are, the more accurate the response you get.
it possible to solve the problem without resorting to filtration, drying and weighing?Of course you can.You need only to write the exact equation of the chemical reaction and know the amount of starting materials.For example, by reacting 10 grams of sodium chloride and 4 g of silver nitrate white precipitate of silver chloride.Required to calculate its mass .Write the reaction equation: NaCl + AgNO3 = NaNO3 + AgCl
Calculate the molar mass of the starting materials.23 + 35.5 = 58.5 g / mol - the molar mass of sodium chloride, 10 / 58.5 = 0.171 mole - such was the amount before the reaction.108 + 14 + 48 = 170 g / mol - the molar mass of silver nitrate, 4/170 = 0.024 mole - an amount of the salt before the reaction was.
You can see that the sodium chloride is in a large excess.From this it follows that all reacted silver nitrate (all 4 grams), is also related to 0.024 mol of sodium chloride.So how much eventually formed silver chloride?Calculate its molar mass .108 + 35.5 = 143.5 g / mol.Now we perform calculations: 143,5 * 4/170 = 3,376 grams of silver chloride.Or, considering rounding 3.38 grams.The problem is solved.
If you do not require more precision can be made round the counting results, the molecular weight, etc.