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Question 11 Mark
Define saturated solution.
Answer
The maximum amount of solvent that can dissolve in 100 gm of solvent at a certain temperature is called saturated solution.
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Question 21 Mark
Write names of solute and solvent present in sodium amalgam solution.
Answer
The solute is mercury $( Hg )$ and sodium (Na) is solvent.
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Question 31 Mark
Explain the reason for the solution of chloroform and acetone showing negative deviation from Raoult's law.
Answer
Chloroform molecule cannot form hydrogen bonds with acetone molecule, hence the solution of chloroform and acetone shows negative deviation from Raoult's law:

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Question 41 Mark
Why do aquatic animals lives more easily in cold water than in hot water?
Answer
As the temperature increases the solubility of gases in water decreases, therefore, the amount of oxygen in hot water is less, hence the aquatic animals remains more easily in cold water than in hot water.
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Question 51 Mark
In case of swelling in the throat, it is advisable to gargle with normal salt water, why?
Answer
Salt water is hypertonic, due to which it expels the factor causing strain in the throat.
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Question 61 Mark
Rubbing isopropyl alcohol gives a cooling sensation on the skin, why?
Answer
Isopropyl alcohol is volatile, hence it absorbs latent heat from skin and gets converted in to vapour due to which cooling is felt.
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Question 81 Mark
Explain the relationship between molality and boiling point elevation.
Answer
Boiling point of elevation and molality are proportional to each other.
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Question 91 Mark
What will happen when the outer shell of the egg is removed and it is placed in a saturated solution of salt $( NaCl )$ ?
Answer
The process of osmosis will take place in egg due to which it shrinks.
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Question 101 Mark
The molal depression $\left( K _{ f }\right)$ constant for water is $1.86 K kg mol ^{-1}$, what does it meant?
Answer
For water, $K _{ f }=1.86 K kg mol ^{-1}$ means that when I mole of non-volatile solute is dissolved in 1 kg of solvent, then the freezing point of water decreases by 1.86 K .
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Question 111 Mark
Will equimolar solutions of sugar and KCl becomes isomotic or not? Why?
Answer
Equimolar solutions of sugar and KCl are not isosmotic because KCl dissociates to give two ions whereas sugar does not dissociates.
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Question 121 Mark
When does reverse osmosis occur?
Answer
When more pressure is applied on the solution than the osmotic pressure, reverse osmosis occurs.
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Question 131 Mark
Explain the relation between boiling point of elevation of solution ( $\Delta T _{ b }$ ) and molar mass of solute.
Answer
$\Delta T_b$ is inversely proportional to the molar mass of solute.
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Question 141 Mark
What will be the effect of adding a little glucose to water on its vapour pressure?
Answer
By adding glucose, the vapour pressure of water will reduce because glucose is a non-volatile substance.
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Question 151 Mark
What is the relationship between the degree of dissociation of solute in the solution and van't Hoff factor?
Answer
$\alpha=\frac{i-1}{n-1}, \alpha=$ Degree of dissociation, $n=$ Number of particles obtained by dissociation $i=$ van't Hoff factor
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Question 161 Mark
Ammonia bottle is cooled before opening, why?
Answer
By cooling the ammonia bottle its vapour pressure reduces due to which the liquid ammonia does not come out quickly.
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Question 171 Mark
What is the effect of pressure on solubility of gases?
Answer
On increasing the pressure the solubility of gases in liquids increases.
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Question 181 Mark
If the solubility of nitrogen in water at the same temperature is less than that of hydrogen, then which gas has higher Henry's constant?
Answer
Henry's constant of nitrogen is high because the solubility of a gas $\propto \frac{1}{K_{ H }}\left( K _{ H }=\right.$ Henry's constant).
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Question 191 Mark
The components present in adiabatic mixture cannot be separated by fractional distillation. Why?
Answer
The components present in a mixture in fixed proportions which boils together at a fixed temperature, hence, they can't be separated by fractional distillation.
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Question 201 Mark
Which type of liquids have the tendency to form ideal solution?
Answer
Very dilute solution, almost uniform compositon and polar liquids have the tendency to form ideal solutions.
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Question 211 Mark
Define Henry's law.
Answer
The mole fraction of a gas in solution is proportional to the partial pressure of the gas present above, that is, the partial pressure of a gas in the vapour state is proportional to the mole fraction of the gas in the solution. This is called Henry's law.
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Question 221 Mark
What will be the effect on the solubility of gases in liquids when the temperature is increased?
Answer
On increasing the temperature, the solubility of gases in liquids decreases.
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Question 231 Mark
Which one has higher concentration among one molal or one molar aqueous solution?
Answer
One molar solution.
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Question 241 Mark
Why does molality has been given more importance than molarity?
Answer
Molality is given more importance than molarity because molality does not depend on temperature.
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Question 251 Mark
What is meant by volume concentration of $H _2 O _2$ ?
Answer
The volume of oxygen obtained at NTP from the dissociation of one volume of $H _2 O _2$ solution is called its volume concentration.
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Question 261 Mark
What will be the effect on molarity by increasing the temperature of the solution?
Answer
On increasing the temperature of the solution, molarity decreases because the volume of solution increases.
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Question 271 Mark
What is the relation between molality of any substance and mole fraction of solute for an aqueous solution?
Answer
$ \text { Mole fraction of solute }=\frac{m}{m+55.5}$
$m=\text { molality, moles of } 1000 g \text { water }=\frac{1000}{18}=55.5 $
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Question 281 Mark
What is meant by 0.2 molal solution?
Answer
0.2 molal solution means that 0.2 molal solute is dissolved in $1000 g(1 kg)$ of solvent.
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Question 291 Mark
If 2 g of sugar is dissolved in 100 g of water, the solution made is X and on adding 2 g urea to 100 g water, the solution obtained is Y , which solution has greater boiling point elevation and why?
Answer
The boiling point elevation will be more in solution Y because the molecular weight of urea is less than the molecular weight of sugar, hence the molality of solution Y will be more than the molality of solution X and the boiling point elevation is proportional to the molality.
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Question 301 Mark
Why does it takes more time to make icecream with milk with dissolved sugar than to make ice-cream from only milk?
Answer
On adding sugar to milk, the freezing point of milk becomes molar (freezing point depression), that is, the milk will freeze at a lower temperature than before, hence it takes more time to make ice-cream.
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Question 311 Mark
Cutting onion after cooling it in refrigerator instead of cutting it at room temperature results in less tears. Why?
Answer
When onion is cooled, the vapour pressure of the volatile liquids present in it decreases which causes tears, hence their evaporation reduces. Hence, tears come less when cutting a cold onion.
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Question 321 Mark
What a anoxia?
Answer
Anoxia is a type of disease which is generally found in people living at high altitude. In this, the concentration of oxygen in the blood and tissues of people decreases, hence they become weak and their thinking ability also decreases.
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Question 331 Mark
What will be the effect of temperature on the solubility of NaOH in water?
Answer
Formation of solution of NaOH in water is an exothermic process, hence according to Le Chatelier's law, on increasing the temperature for exothermic process, the equilibrium goes in the reverse direction, that is the solubility of NaOH will decrease.
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Question 341 Mark
When a cold bottle of a soft drink which is carbonated is opened, the gas bubbles comes out rapidly. Why?
Answer
A carbonated soft drink bottle is filled with carbon di$-$oxide $(CO_2)$ gas at high pressure. When the lid of the bottle is opened, this gas flows out rapidly from high pressure to low pressure, hence bubbles are seen coming out.
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1 Marks Question - Chemistry STD 12 Science Questions - Vidyadip