Concentration

Question 1 What is meant by the concentration of a solution?

Question 2 How much water should be added to 15g of salt to obtain 15 per cent salt solution?

Question 3 Calculate the concentration of a solution which contains 2.5g of salt dissolved in 50g of water?

Question 4 What does a 15% alcohol solution means?

Question 5 If 25mL of acetone is present in 150ml of its aqueous solution,calculate the concentration of solution?

Question 6 What is a saturated solution.Give example?

Question 7 What is an unsaturated solution.Give example?

Question 8 What is the effect of heating on a saturated solution?

Question 9 Define the term solubility?

Question 10 What is the effect of temperature on solubility?

Question 11 What is the effect of pressure on solubility ?

Question 12 21.5 g of sodium chloride dissolves in 60g of water at 25°C.Calculate the solubility of sodium chloride in water at that temperature?

Concentration of a Solution
The concentration of a solution is the amount of solute present in a given quantity of the solution.
The solution having small amount of solute is called Dilute Solution.

The solution having large amount of solute is called Concentrated Solution.

The concentration of a solution is defined as mass of solute in grams present in 100 g of the solution.

For Ex:10% solution of NaCl (10 g of NaCl + 90 g of water)

                                          Mass of Solute

Concentration of solution =———————— * 100

                                           Mass of solution
Mass of solution=Mass of Solute+Mass of solvent

                                                          volume of Solute

Concentration of solution =———————— * 100

                                       volume of solution

Saturated Solution-A solution in which no more quantity of solute can be dissolved at a given temperature.

Saturated solution contains maximum amount of solute which can be dissolved in it at a given temperature.

Unsaturated Solution – A solution in which more quantity of solute can be dissolved at a given temperature.

In order to test whether a given solution is saturated or not,we should add some more solute to this solution and try to dissolve it by stirring.If it does not dissolve,then it will be a saturated solution but if it dissolve,the it will be an unsaturated solution.

If a saturated solution at particular temperature is heated to a higher temperature,then it becomes unsaturated.

This is because the solubility of solute increases on heating and more of solute can be dissolved on raising the temperature of the solution.

If a saturated solution is cooled to lower temperature then some of its dissolved solute will separate out in the form of solid crystals.This is because the solubility of solute in the solution decreases on cooling.

SOLUBILITY
The maximum amount of a solute which can be dissolved in 100 g of a solvent at a specified temperature is known as the solubility of that solute in that solvent.

For Ex:36 g of NaCl can be dissolved in 100 g of water at 20°C therefore solubility of NaCl in water is 36 g at 20°C

In order to calculate the solubility of a substance,we have to find the mass of substance dissolved in 100g of water.

Effect of temperature and pressure on solubility
1) The solubility of solids in liquids usually increases on increasing the temperature and decreases on decreasing the temperature.

2)The solubility of solids in liquid remains unaffected by the changes in pressure.

3)The solubility of gases in liquid usually decreases on increasing the temperature and increases on decreasing the temperature.

4)The solubility of gases in liquid increases on increasing the pressure and decreases on decreasing the pressure.

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