Question

Part C

A sucrose solution is prepared to a final concentration of 0.280 M . Convert this value into terms of g/L, molality, and mass % (molecular weight, MWsucrose = 342.296 g/mol ; density, ρsol′n = 1.02 g/mL ; mass of water, mwat = 924.2 g ). Note that the mass of solute is included in the density of the solution.

Express the concentrations in grams per liter, molality, and mass percent to three significant figures separated by commas.

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Sucrose concentrations =

.

  g/L, m, %  

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Gravimetric analysis

Gravimetric analysis is a technique by which information is obtained based on massed values. One application of gravimetric analysis can allow the solubility of a solid to be determined. This is achieved by adding a known mass of solid to solution, then collecting and massing the amount precipitated in order to discover how much had dissolved into a known volume of solution. Alternatively, it can be used to identify an unknown solid by determining the solubility in g/mL, then cross referencing against a list of known solubility values.

To observe how such a technique works, select Potassium chromate as the solute in the PhET simulation. Slide both the Solute Amount and Solution Volume to the lowest possible values (0.00 moland 0.20 L). Then, begin adding potassium chromate solute by sliding the Solute Amount scale bar upward. This represents adding solute to a solution. Once the amount of solute surpasses 0.67 mol, additional solute collects at the bottom of the beaker as a precipitate. This precipitate can then be collected, dried, and massed. Then, by determining the difference between total mass and precipitated mass, the dissolved mass can be found. Dividing dissolved mass by solution volume would provide a usable concentration value that indicates solubility.

Part D

Suppose 237.6 mg of PbCl2 was added to 15.0 mL of water in a flask, and the solution was allowed to reach equilibrium at 20.0 oC. Some solute remained at the bottom of the flask after equilibrium, and the solution was filtered to collect the remaining PbCl2, which had a mass of 83.6 mg . What is the solubility of PbCl2 (in g/L)?

Express the concentration in grams per liter to three significant figures.

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Solubility of PbCl2 =

  g/L  

Answer 1

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