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 ;
- 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 ;
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 .
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 :
- Starch solution
Q#6 : Why do we stir paints thoroughly before using ?
We stir paints thoroughly before using ;
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 .
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.
- Ionic solids and polar covalent compounds are soluble in polar solvents e.g. KCl , Na₂CO₃ , CuSO4 are all soluble in Water .
- 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 :
- solvent-solvent and
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.