Chemistry M.C.Q (1 Marks)

2. Raoult’s law

1. Two different solutions of sucrose of same molality prepared in different solvents will have the same depression in freezing point.

Explanation:

Tf = Kfm Since Kf values depend upon the nature of solvent, the depression in freezing point of the solution would not be the same.

1. Smoke is carbon dispersed in air.

Explanation:

Smoke is carbon (solid particle) dispersed in air. It is the type of solid in gas type of solution.

1. vapour pressure in container (A) is more than that in container (B).

Explanation:

Since NaCl is a non-volatile solute, it will reduce vapour pressure of the solution. Hence, vapour pressure of pure water in container A is more than in container B.

4. All of the above

Explanation:

The rate of vapourization of water depends on the temperature and surface area. 

The kinetic energy of molecules depends on the temperature of the water.

Increasing temperature or surface area increases the rate of evaporation and vice-versa.

3. m, x

2. Vapour pressure only depends on temperature and not on the nature of substance.

Explanation:

The vapour pressure depends on the temperature and the nature of substance.

1. Ideal

Explanation:

Due to absence of polarity, benzene and toluene dont have any interaction forces so they dont show any deviation and forms ideal solutions.

3. Its boiling point increases.

1. At specific composition methanol-acetone mixture will form minimum boiling azeotrope and will show positive deviation from Raoult’s law.

Explanation:

At specific composition methanol-acetone mixture will show positive deviation from Raoulfs law as it has lesser interactions than methanol- methanol and acetone-acetone interactions. Hence it forms minimum boiling azeotrope.

4. Mercury

4. ppm

1. Saturated

Explanation:

The maximum number of moles of solute that can be dissolved in a given volume of solution represents the solubility of solution.

A solution with the maximum possible amount of solute is saturated.

Hence a saturated solution must be prepared to determine the solubility of a solute in water,

1. Solid in gas solution

Explanation:

Solid in gaseous solution is an example of camphor in N2 gas. Gaseous solution refers to a solution in which the solvent is gaseous. Other gaseous solutions include air (O2 + N2), iodine vapors in air, humidity in air, and so on.

2. Molar solution

Explanation:

Molar concentration is a measure of the concentration of a solute in a solution and its unit is mol L⁻¹. Molarity is a method to express the concentration of a solution. It is defined as the number of moles of solute dissolved per liter of solution.

Hence, when 1 mole of a substance is present in 1L of the solution, it is known as a molar solution.

1. Sugar-water mixture

1. 91.8g

2. Toluene and Benzene

Explanation:

Toluene and Benzene are very similar molecules  and hence are ideal solution,  others are solutions showing positive deviation (Theory based. To be memorized.) 

2. Nature of the solvent.

3. FeCl₃​, 30% ionised

Explanation:

Soluten a i = [1 + (n -1)a]

KCl 20.51.5

K₂​SO_4​ 30.41.8 

FeCl₃​ 40.31.9

SnCl₄​ 50.21.8

1. A non volatile solid is dissolved in a volatile liquid.
2. A non volatile liquid is dissolved in another volatile liquid.

Explanation:

Colligative properties are observed when a non-volatile solid or liquid are dissolved in a volatile liquid.

2. Depression in freezing point of snow.

3. The forces of attractions between like molecules are identical with those between unlike molecules.

Explanation:

When the forces of attractions between like molecules are identical with those between unlike molecules, Raoult's law is obeyed by each constituent of a binary liquid solution.

In such case, the total vapour pressure of the solution is the sum of the partial vapour pressures of components of the solution.

2. Positive deviation from Raoult’s Law.

2. Solute

Explanation:

A concentrated solution contains the maximum amount of solute that can be dissolved because solubility depends on temperature, a solution that is concentrated at one temperature may not be concentrated at a higher temperature.

2. Melting point of solute

Explanation:

Vapour pressure of a dilute solution depends upon the temperature, mole fraction, and degree of dissociation of solute and independent of the melting point of solute.

2. Increase the boiling point.

3. These will form minimum boiling azeotrope.
4. These will not form ideal solution.

Explanation:

In a mixture of benzene and toluene intermolecular forces between benzene and toluene molecules would be nearly of the same strength as those of two benzene molecules and two toluene molecules separately. The solution will, therefore, form an ideal solution & obey Raoult’s law. So, the option (iii) & (iv) is not true.

2. Osmotic pressure is same.
3. Solute and solvent may or may not be same.

Explanation:

For isotonic solutions osmotic pressure is same, solute or solvent may not be same.

2. In reverse osmosis, solvent molecules move through a semipermeable membrane from a region of lower concentration of solute to a region of higher concentration.

Explanation:

In reverse osmosis solvent molecules move through a semipermeable membrane from a region of higher concentration of solute to a region of lower concentration, therefore the given statement at (ii) is false.

3. The van't Hoff factor

Explanation:

The van't Hoff factor is the ratio of the actual value of a colligative property to the value calculated. It is assumed that the substance is a nonelectroyte.

It can also be represented as the ratio of actual number of particles to the number of particles for no ionization.

3. NaF

4. Potassium dichromate

Explanation:

The primary standard is a compound of  sufficient purity from which standard solutions of known normalities can be prepared by direct weighing of it and diluting to a defined volume of solution.

Potassium Dichromate(K₂​Cr₂​O₇​) is suitable to be used as a primary standard. It cannot be obtained in very pure form. It readily reacts with any traces of organic material or any other reducing substance in wate

4. Powdered sugar in hot water.

Explanation:

Since the solution is cool to touch, the dissolution is endothermic. Therefore, high temperature will favour dissolution. Further, powdered sugar has large surface area and is favourable for dissolution.

1. Increases with increase in temperature.

Explanation:

Value of Henry’s constant increases with increase in temperature.

4. HCI

Explanation:

The following substances were all dissolved in 100 grams of water at 290K to produce saturated solutions. If the solution is heated to 310K, HCl will have a decrease in its solubility. HCl is a gas. The solubility of a gas in a solution is inversely proportional to the absolute temperature. With increase in the temperature, the solubility of a gas decreases.

4. Dissolving salt in the water

Explanation:

Vapour pressure is a surface phenomenon, when the surface area is more, vapour pressure will be more. When we add solute, what we do is we decrease the vapour pressure of solvent because same of the salt ions will be present at the solvent surface, thus taking place of same of the solvent particles which were actively participating in maintain, that previous high value of vapour pressure. So, the equilibrium vapour pressure value decreases. Thus, dissolving salt in water results in decreasing of equilibrium vapour pressure.

2. Partial pressure

Explanation:

Partial pressure is the pressure exerted by a single component in a gaseous mixture if it exists alone in the same volume.

2. Water will move from side (B) to side (A) if a pressure greater than osmotic pressure is applied on piston (B).

Explanation:

Water will move from side (B) to side (A) if pressure greater than osmotic pressure is applied on piston (B) due to reverse osmosis.

1. Mole fraction.

Explanation:

It is mole fraction (x) which is useful in relating concentration of solution with its vapour pressure. For example according to Rault's law in a binary solution of two volatile liquids, p₁ = x₁ p⁰₁ where p₁ is vapour pressure of component 1, and x₁ is its mole fraction in solution, p⁰₁ denotes the vapour pressure of pure solvent.

3. Equal to the rate of crytallisation

Explanation:

Crystallization is the process of the formation of solid crystals precipitating from a solution.

In an unsaturated solution, the rate of dissolution of a solute in a volatile liquid solvent is greater than the rate of crystallization. 

In a supersaturated solution, the rate of dissolution of a solute in a volatile liquid solvent is less than the rate of crystallization.

At equilibrium, the rate of dissolution of a solute in a volatile liquid solvent is equal to the rate of crystallization.

1. Al₂​(SO₄​)_3​

4. It loses water due to osmosis.

Explanation:

Water starts moving out of mango (lower concentration) to the salt solution (higher concentration) due to osmosis.

4. 0.016

Explanation:

Apply the relation, M₁V₁ = M₂V₂

Given, M₁ = 0.02M, V₁ = 4L, M₂ = ?, V₂ = 5L

Therefore, 0.02 × 4L = M₂ × 5L

 M₂ = 0.08/5

=0.016M

2. Low atmospheric pressure.

Explanation:

At high altitude the atmospheric pressure is decreased &, due to low atmospheric pressure the solubility of oxygen in blood and tissues is reduced.

4. The solute precipitates out of the solution.

Explanation:

Solute particles leave the solution and form a crystalline precipitate when a solute crystal is added to a supersaturated solution. Seeding refers to the addition of the solute crystal.