Solutions

9th chemistry chapter 6 solved exercise short questions

Solved exercise short questions :

Q#1 : Why suspensions and solutions do not show tyndall effect , while colloids do ?

Suspensions and solutions do not show tyndall effect because ;

Reason :

• In suspensions , particles are so big that light is blocked and difficult to pass .
• In solutions , particles are so small that they cannot scatter the rays of light .

But Colloids can show tyndall effects ;

Reason:

because particles scatter the path of light .

Q#2 : What is the reason for the difference between solutions , colloids and suspensions ?

The reason for the difference between solutions , colloids and suspensions is size of particles of solute.

• Solute particles in solutions are very small but particles in suspensions are very larger . On the other hand , colloids have particles smaller than those of suspensions but larger than solution particles .

Q#3 : Why the suspension does not form a homogeneous mixture ?

Suspension is a heterogeneous mixture of undissolved particles in a given medium .

Reason :

Particles are big enough to be seen with naked eye. These particles are so big that they settle down at bottom .

That is why ; suspensions cannot form a homogeneous mixture . To form a homogeneous mixture particles should be dissolved and form a uniform mixture .

Q#4 : How will you test weather given solution is a colloidal solution or not ?

Tyndall Effect Test :

We will pass light through the solution, if the given solution scatters the light then its a colloidal solution . But if it does not scatter light than it is not a colloidal solution .

Hence , scattering of light or tyndall effect is the main characteristic which distinguishes colloids from solutions.

Q#5 : Classify the following into true solution and colloidal solution :

True Solutions :

• Glucose solution
• Copper sulphate solution
• Silver nitrate solution

Colloidal Solutions :

• Blood
• Starch solution
• Toothpaste

Q#6 : Why do we stir paints thoroughly before using ?

We stir paints thoroughly before using ;

Reason :

Because paint is a suspension which is a heterogeneous mixture of un dissolved particles in a given medium .

Particles are big enough to be seen with naked eye and settle down after sometime .

• Whenever, we use paints we stir it thoroughly so that the settled down particles will suspend again in mixture and will be easy to use .

Q#7 : Which of the following will scatter light and why ?

( sugar solution , soap solution and milk solution )

Soap solution will scatter light among all .

Reason :

Because soap solution is a good example of colloidal solution .

Q#8 : What do you mean , like dissolve like ? Explain with example .

” Like dissolve Like “ is the general principle of solubility , which means polar solvents dissolve polar solutes while non-polar solvents dissolve non-polar solutes.

Example :

1. Ionic solids and polar covalent compounds are soluble in polar solvents e.g. KCl , Na₂CO₃ , CuSO4 are all soluble in Water .
2. Non-polar covalent compounds are not soluble in water such as Benzene and petrol are insoluble in water .

Q#9 : How does nature of attractive forces of solute-solute and solvent-solvent affect the solubility ?

Solution formation depends upon the relative strength of attractive forces between :

• solute-solute
• solvent-solvent and
• solute-solvent

If forces between solute-solvent particles overcome the solute-solute attraction , solute dissolves and form a solution and vice versa.

Q#10 : How can you explain the solute-solvent interaction to prepare a NaCl solution ?

NaCl is an ionic compound while water is a polar compound .

• When NaCl is added in water , it dissolves readily because the attractive forces between the ions of NaCl and polar molecules of water are stronger enough to overcome the attractive forces between Na+ and Cl- ions in solid NaCl crystal .

Q#11 : Justify with an example that solubility of a salt increases with the increase in temperature .

Solubility of some salts which are usually endothermic in nature , increases with the increase in temperature.

Example : KCl , KNO₃ , NaNO₃ etc.

Q#12 : What do you mean by volume / volume % ?

It is the volume in cm³ of a solute dissolved in 100 cm³ of the solution .

For example :

30 % v/v of alcohol solution means 30cm³ of alcohol dissolved in sufficient amount of water , so that the total amount of solution becomes 100cm³.

Formula: