If a saturated solution with Pb(NO3)2 at 60ºC is cooled to 10ºC, how much Pb(NO3)2 will settle out of the solution?

  1. Solubility is a function of temperature.
  2. For lead (II) nitrate, solubility increases with an increase in temperature.
  3. A decrease in temperature will mean that lead (II) nitrate will settle out.
  4. The solubility values (in g/100 g of water) are 91.6 and 46.2 at 60 degrees and 10 degrees Celsius.
  5. The residual 45.4 g /100 g of water will settle out.

Expert Answers

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A saturated solution means that the solute has been added to its solubility limit and that no more solute can be added to that particular solvent at that temperature. Any extra addition will show up as residue.

Solubility is a measure of how much of a substance can be added...

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A saturated solution means that the solute has been added to its solubility limit and that no more solute can be added to that particular solvent at that temperature. Any extra addition will show up as residue.

Solubility is a measure of how much of a substance can be added to a solvent (generally, water) at a given temperature. It is a function of the temperature and for many solutes, the solubility increases as the temperature increases. This means that more and more solute can be added with an increase in temperature. Conversely, if the temperature were to reduce, the dissolved solute will be released from the solution and it will settle out of the solution.

For such a scenario, a solubility curve is very useful. It is a graph between the amount of solute dissolved in the solvent (generally 100 g of water) at the Y-axis and the temperature (in degrees Celsius) at the x-axis.

For lead (II) nitrate, the solubility values are:

at 60 degrees Celsius: 91.6 g/100 g of water

at 10 degrees Celsius: 46.2 g/100 g of water

Thus, at 60 degrees Celsius, a saturated solution of lead (II) nitrate will contain 91.6 g of the solute per 100 g of water. And at 10 degrees Celsius, it will contain only 46.2 g of solute per 100 g of water. The difference (91.6-46.2) of 45.4 g shall settle down at the bottom fo the solution for every 100 g of water.

Given the actual volume of the solution, we can calculate the total amount of the solute that will settle out.

Hope this helps.

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