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Define solution. Give examples of gas, solid and liquid solutions.
Ans. Solution:
"A solution is a homogeneous mixture of two or more substances. One substance is called solvent and all others are called solutes."
(2) The air we breathe is a gas solution of several gases
Liquid Solution:
Sugar dissolved in water is an example of a liquid solution.
Solid Solution: The brass is a solid solution of Zn and Cu.
How the physical state of a solution is defined/determined?
Ans. Solutions are found in all three physical states i.e. solids, liquids and gases. The physical state of a solution depends upon the physical state of its solvent. Thus, the physical state of a solution can be determined following:
(1) If solvent is a liquid, the physical state of a Solution = Solvent Solute(s)
Examples:
Following are some most common examples of solutions.
(1) Gas Solution
How can we distinguish between a solution and a pure liquid by ordinary physical methods?
The simplest way to distinguish between a solution and a pure liquid is evaporation phenomenon. The liquid which evaporates completely, leaving no residue, is a pure compound, while a liquid which leaves behind a residue on evaporation a solution.
(iv) a solution considered a mixture?
Ans. A solution is considered as a mixture because both the solutions and the mixtures constituents can be separated by physical means.
Distinguish between the following pairs as compound or solution.
solution will be liquid.
e.g. air
(2)If solvent is a solid, its physical state will be solid.
e.g. sugar solution
(3) If solvent is a gas, the solution will be called gas (a)
Water and salt solution
b Vinegar and benzene
(c Carbonated drink and acetone
Water and salt solution
Solutionb) Vinegar and benzene
Solution
(c) Carbonated drink and acetone Solution
(vi) What is an alloy? Why an alloy is considered as a mixture?
Ans. Alloy: "Alloy is a mixture solid into solids"
Example: Brass is a mixture of zinc (Zn) and copper (Cu)
Why an Alloy is considered as a Mixture: Although an alloy cannot be separated by physical means, yet it is considered a mixture. It is due to the following two reasons:
(1) It shows the properties of its component
(2) It has a variable composition.
(vii) Define solute and solvent with examples.
Ans. Solute: "The component of a solution which is present in smaller quantity is called a solute.
A solute is dissolved in a solvent to make a solution.
Examples: Salt solution is made by dissolving salt in water. So, in a salt solution, salt is a solute and water is solvent.
Solvent: "The component of a solution which is present in large quantity is called a solvent.
Solvent always dissolves solutes.
Examples: In soft drinks, water is solvent while other substances like sugar, salts and Co, are solutes.
(viii) Differentiate between saturated and unsaturated solution?
Ans. Saturated Solution:
"A solution containing maximum amount of a solute at given temperature is called a saturated solution."
Unsaturated Solution:
"A solution which contains less amount of solute than that which is required to saturate it at a given temperature is called an unsaturated solution Such solutions have the capacity to dissolve more solute to become a saturated solution.
(ix) What is meant by supersaturated solution? How it can be prepared?
Ans. Supersaturated Solution:
"The solution that is more concentrated than a saturated solution is known as a supersaturated solution.
Preparation of a Supersaturated Solution: Procedure:
An easy way to get a supersaturated solution is to prepare a saturated solution at high temperature. It is then cooled to a temperature where excess solute crystallizes out and leaves behind a supersaturated solution.
Example:
A saturated solution of sodium thiosulphate (Na2S,O) in water at 20°C has 20.9g of salt per 100 cm of water.
Less than this amount of salt per 100 cm of water at 20°C will be an unsaturated solution. A solution having more amount than 20.9g of salt per 100 cm of water at 20°C will be a supersaturated solution
(i) Differentiate between a dilute and a concentrated solution. Give one example.
Ans. Dilute Solution:
Dilute solutions those which contain relatively small amount of dissolved solute in the solution.
Concentrated Solution: "Concentrated solutions are those which contain relatively large amount of dissolved solute in the solution
Common Example:
Brine is a concentrated solution of common salt in water.
(ii) Define % m/m. What is meant by 10% m/m sugar(v) Why is the formula of solute necessary for the calculation of the molarity of the solution?
Ans. To calculate the molarity of the given solution, molar mass of a solute is necessary. This is because molar mass is used to convert the mass of solute into moles of solute.
(viil) Define solubility. What is the effect of temperature on solubility?
Ans. Solubility:
"The number of grams of the solute dissolved in 100g of solvent to prepare a saturated solution at a particular temperature is called solubility.
Effect of Temperature on Solubility Temperature has major effect on the solubility of most of the solutes. Generally it seems that solubility increases with the increase of temperature, but it is not always true.
(iii) Which three events must happen before dissolution of a solute into a solvent?
Dissolution of a Solute into a Solvent: To dissolve one substance (solute) in another substance (solvent) following three events must occur:
1) Solute particles must separate from each other.
(2) Solvent particles must separate to provide space for solute particles
(3) Solute and solvent particles must attract and mix up
(iv) Explain the conditions under which the formation of a solution is possible?
Ans. For the formation of a solution, there are following two possibilities:
(1) If the new forces i.e. forces between solute solvent particles overcome the solute-solute attractive forces, then the solute dissolves in a solvent and makes a solution.
(2) If the solvent-solvent forces are stronger than the solute-solute forces, in this case solution formation is also possible.
(v) What will happen if the solute-solute forces are stronger than those of solute-solvent forces?
Ans. If the solute solute forces are stronger than those of solute-solvent forces, then solute remain insoluble and solution is not formed.The particles of suspensions are so big that the light is blocked and is not scattered.
On the other hand the particles of solutions are so small that they can not scatter the rays of light.
That is why both suspensions and solutions do not show Tyndall effect. But the particles of colloids can scatter the rays of light and exhibit the Tyndall effect.
(vii) Write two/four characteristics of a colloid.
Ans. Characteristics of a Colloid:
(1) The particles are large consisting of many atoms ions or molecules.
(2) A colloid appears to be a homogeneous but actually it is a heterogeneous mixture. Hence they are not true solutions Particles do not settle down for a long time, therefore, colloids are quite stable.
(3) Particles are large but can't be seen with naked eye.
(4) Although particles are big but they can pass through a filter paper.
(5) Particles scatter the path of light rays thus emitting the beam of light i.e. exhibit the Tyndall effect.
(viii) Write two/four properties of a suspension.
Ans. Characteristics of a Suspension:
(1) The particles are of largest size. They are larger than 10 cm in diameter.
(2) Particles remain un-dissolved and forma heterogeneous mixture. Particles settle down after sometime.
(3) Particles are big enough to be seen with naked eye.
(4) Solute particles cannot pass through filter paper.
(5) Particles are so big that light is blocked and difficult to pass.
Classify the following into true solution
Ans.
colloidal solution:
blood, starch solution, glucose solution, tooth paste, copper sulphate solution, silver nitrate solution
Real Solution/True Solution:
Glucose solution, copper sulphate solution and silver nitrate solution.
Colloidal solution:
Blood and starch solution.
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