Define Saturated solutions, Solubility and solubility curve.

Define Saturated solutions, Solubility and solubility curve.

Saturated solutions:

A saturated solution is a solution that contains the maximum amount of solute that is capable of being dissolved. 

A saturated solution is a solution in which no more solute will dissolve at a given temperature.

 In chemistry to define a solution in which no more solute can be dissolved in the solvent

Solubility:

Solubility is the ability of a solid, liquid, or gaseous chemical substance to dissolve in solvent and form a solution.

The solubility of a substance tells us how many grams of it will dissolve in 100g of water at a certain temperature.

Solubility curves:

A solubility curve is a graph of solubility, measured in g/100 g water, against temperature in °C.

A solubility curve is a data represented as graph relating solubility to temperature. 

Solubility curves

Saturated solutions

Only a certain amount of solute can dissolve in a particular volume of solvent at any given temperature. This amount varies from solute to solute.

A saturated solution is a solution in which no more solute will dissolve at a given temperature.

 

We can describe how well a solute dissolve in water by its solubility

The solubility of a substance tells us how many grams of it will dissolve in 100g of water at a certain temperature.

For example, the solubility of sodium chloride is 36g per 100g of water at 25°C.

 

 

Experiment 22.5 The solubility curve of potassium nitrate

Measure out 10 g of potassium nitrate.

Heat some water to 70 °C in a small beaker.

Transfer 10 cm3 of the hot water to a boiling tube.

Now add the 10 g of potassium nitrate to the boiling tube, and stir with a glass rod.

This should form a solution that is almost saturated.

Let the tube cool down. Note the temperature when the first crystals appear.

 

At what temperature does the solution become saturated? Now add another 5 cm³ of water to the boiling tube to make the volume up to15 cm. Stir the solution so that the potassium nitrate re-dissolves. Warm the tube in a water bath if necessary. Again cool the tube down and record the temperature at which the solid appears. Repeat for total volumes of 20, 25 and 30 cm' of water

How will you convert your results into solubility's per 100g of water?

Remember 100 cm3 of water has a mass of 100g. (You could use a spreadsheet)

Record your results and solubility's, in g/100 g of water, in a table

Think about how to make your results as reliable as possible.

Once you have converted your results to solubility's per 100g of water draw a solubility curve for potassium nitrate.

How does the solubility of potassium nitrate vary with temperature?

 

Solubility curves enable you to

Redd the solubility at temperatures you didn't investigate.

Scale up or down to work out how much solid dissolves in any volume of water.

work Out what mass of solid is crystalized from a saturated Solution cooling between two given temperatures.

 

 

Example (using the graph opposite)

 

 

 

 

 

 

 

 

 

 

 

 

 

Class Assessment

 

1.   The --------------- of a substance tells us how many grams of it will dissolve in 100g of water at a certain temperature.

A. solubility

B.  ion

C. salts  

 

2.   Special desalination -------------- can take most of the dissolved salts out of sea water.

A.  methane

B.  soap

C. plants

 

3.   Water is -------------------, then cooled and condensed to separate it from dissolved solids.

A.  evaporated

B.  filtered

C. Cooled

 

4.   the solubility of sodium chloride is 36g per ---------- of water at 25°C.

A. 100g

B.  88g

C. 78g

 

5.   100 cm3 of ------------- has a mass of 100g.

A.  water  

B.  sol

C. alcohol

 

6.   --------------------------- is used in Middle East countries.

A.  Evaporation 

B. Desalination

C. Precipitation

 

 

1.   Only a certain amount of solute can dissolve in a particular volume of solvent at any given temperature.

A. True

B.  False

2.   A saturated solution is a solution in which no more solute will dissolve at a given temperature.

A.  True

B. False

3.   The process used in some desalination plants is based on distillation.

A. True

B.  False

4.   The calcium ions get stuck on the resin.

A. True

B.  False

5.   Solubility curves enable you to read the solubility at temperatures you didn't investigate.

A. True

B.  False