Chemistry: CUET Mock Test - 10 - CUET MCQ

An electrolytic cell is a type of electrochemical cell. An electrolytic cell converts electrical energy into chemical energy. Electrons flow from anode to cathode through the external supply in an electrolytic cell. In the solution, only ions flow and not the electrons.

A salt bridge is a junction that connects the anodic and cathodic compartments in a cell or electrolytic solution. It maintains electrical neutrality within the internal circuit, preventing the cell from rapidly running its reaction to equilibrium.

Electrode potential is the tendency of an electrode to accept or to lose electrons. Electrode potential depends on the nature of the electrode, temperature of the solution and the concentration of metal ions in the solution. It doesn’t depend on the size of the electrode.

A half-cell is half of an electrochemical cell (electrolytic or galvanic), where either oxidation or reduction occurs. At equilibrium, there is no transfer of electrons across the half cells. Therefore, the potential difference between them is nil.

On association of solute molecules, the number of particles in a solution is reduced. Since, colligative properties are directly proportional to the number of particles in a solution, the colligative properties reduce. The molecular mass of the solute is inversely proportional to its colligative properties. Therefore, solutes that associate in water have a higher molar mass than its value calculated theoretically.

The Van’t Hoff factor is less than 1 for solutes that dissociate in solution. In the given list, only sodium chloride dissociates in water whereas the remaining carboxylic acids associate in benzene. Hence, the value of the Van’t Hoff factor is lesser than 1 for a solution of sodium chloride in water.

Given,
Depression in freezing point(ΔT) = -0.2 °C
Molality of the solution(m) = 0.1 m
Freezing point depression constant (Kf) = 4.0 °C m^-1
Let the Van’t Hoff factor = i
We know that, ΔT = i x K_f x m
0.2 = i x 4 x 0.1
i = 0.2/0.4 = 0.5
Therefore, the ratio between the normal mass and abnormal mass, which is equal to the Van’t Hoff factor is equal to 0.5.

KOH→K⁺ + OH^–
(NH₄)₂SO₄→2NH₄⁺ + SO4^2-
K₂CO₃→2K⁺ + CO₃^2-
K₂SO₄→2K⁺ + SO₄^2-
Concentration of particles in 1.0 M KOH solution is minimum (= 2 M). Hence, it will minimum elevation in boiling point.

Given,
Degree of association (α) = 50% = 0.5
Number of molecules associated (n) = 2
Let the Van’t Hoff factor = i
We know that for solutes that associate in solution, i = 1 + ((1/n) -1) x α
= 1 + ((1/2) – 1) x 0.5
= 1 – (0.5 x 0.5)
= 0.75
Therefore, the Van’t Hoff factor is equal to 0.75.

pH = 4 means [H⁺] = 10^-4 M

Total = C (1+α)
Thus, [H⁺] = Cα, i.e., 10^-4 = 2 x α or α = 5 x 10^-5 = 0.00005
i = 1 + α = 1 + 0.00005 = 1.00005.

Van’t Hoff Factor can also be written as the ratio between the total number of moles of particles after association / dissociation and the total number of moles of particles before association / dissociation. Since BaCl₂ completely dissociates(into one Ba2⁺ and two Cl^- ions), the total number of moles after dissociation is equal to 3. Therefore, the Van’t Hoff Factor for BaCl₂ is 3.

Van’t Hoff’s factor (i) is defined as the ratio of the observed colligative property to the calculated colligative property. Since, the abnormal mass for solutes that dissociate is lesser than its normal molar mass, the value of Van’t Hoff’s factor will always be > 1.

Solubility is the maximum amount of solute that can be dissolved in a given solvent at a particular temperature and pressure. It is usually expressed in grams of solute dissolved in 100 grams of the solvent. Any more solute added beyond this forms a supersaturated solution as none of the particles dissolve any more.

When a solution is saturated a thermodynamic equilibrium exists between the undissolved solute and dissolved solute. Since the dissolution process here is mentioned as endothermic increasing and decreasing temperatures will decrease and increase the concentration, respectively, as given by Le Chatelier’s Principle of equilibrium.

CO₂ obeys Henry’s law, which governs the solubility of gases in liquids in relation to its pressure. Henry’s law states that mole fraction of gas in the solution varies directly with its partial pressure over the surface i.e. p ∝ x (mole fraction). The graph is of the form y = mx, a positively sloped straight line passing through the origin.

Henry’s law states that the partial pressure of a gas in vapor phase varies directly with its mole fraction in the solution. At higher altitudes the partial pressure of O2 decreases hence the decrease in its concentration which causes difficulty in breathing.

A solution is made up of two parts, the solute and the solvent. Solvent is present in larger quantity which dissolves a solute. The process of dissolution involves formation of homogeneous bonds between the particles of solvent and solute. E.g. salt-water solution is made by dissolving salt, NaCl (solute) in water (solvent).

The formula for silver chromate is Ag₂CrO₄. On the other hand, silver dichromate is formulated as Ag₂Cr₂O₇. If a compound is represented as A_XB_Y then the solubility product expression is written in terms of its molar concentration as [A⁺]^X [B^–]^Y. Similarly, the solubility product expression for Ag₂CrO₄ is given as [Ag⁺]² [CrO₄^2-]².

Water is a universal solvent. It has the ability to dissolve the greatest number of substances than any other solvent. The highly polar nature accounts for this special feature as the water molecule bears a slightly positively charged hydrogen ion and two highly negatively charged oxygen ions. Since, it becomes attracted to many different types of molecules it is known as the ‘universal solvent’.

Out of the given options calcium chloride is the only salt which releases heat upon dissolving. Barium chloride and ammonium chloride undergo endothermic dissolution which decreases the temperature of water. However, lead chloride is an insoluble salt and does not dissolve.

The dissociation reaction is represented as V₃(PO₄)₅ → 3V⁵⁺ + 5PO₄^3-
If S is the solubility of V⁵⁺ and PO₄^3- ions then K_SP = [3V⁵⁺]³ [5PO₄^3-]⁵, where the square brackets indicate the molar concentrations of the ions in the solution. K_SP can then be written as K_SP = [3S] ³[5S] ⁵ = 3³ x 5⁵ x S⁸ gives K_SP= 84375 x S⁸.
Therefore, on rearranging, S = (K_SP/84375)^1/8.

Given,
Solubility of natural gas, S = 0.8 mole of gas/kg of water = 0.8 molal
Hence, moles of natural gas in mixture, n_NG = 0.8 mole
At NTP, pressure, P_NG = 1.01325 bar
Number of moles of water in 1000 g, nw = mass/molar mass
n_w = 1000g / (18g/mole) = 55.56 mole
Mole fraction of natural gas in the mixture, X_NG = n_NG/ (n_NG + n_w)
X_NG = 0.8/(0.8 + 55.56) = 0.0142
Using Henry’s law P_NG = K_H x X_NG
K_H = P_NG/X_NG = 1.01325 bar/0.0142 = 71.36 bar.

Given,
K_H = 0.00060 mole/kgbar
P_N2 = mole fraction of N₂ x P_air (from Dalton’s law)
Air consists of 79 mole% N₂ and 21 mole% O₂.
P_N2 = 0.79 x 1 bar= 0.79 bar
Henry’s law –P_N2x K_H= solubility of N₂
0.79 bar x 0.00060 (mole/kgbar) = solubility of N₂
Solubility of N₂ = 4.74 x 10^-4 moles of N₂/kg water
Converting moles of N₂ to kg of N₂ :
Solubility of N₂ = 4.74 x 10^-4 mole x 28 kg/mole = 0.0133 kg N₂/kg water = 13.3 g N₂/kg water.

Henry’s law is formulated asp = K_H x X (mole fraction). From this, it is seen that as K_H increases, mole fraction decreases in order to compensate the increase in partial pressure of the gas. Hence, higher the K_H value lower is the solubility. Therefore, argon is less soluble in water than CO₂ at 298 K.

In an equilibrium system of gas dissolved in solvent, when pressure over it is increased more and more gas particles are forced into a smaller volume. This also increases the rate at which they strike the surface of the solvent to enter it. Consequently, more gas dissolves with increasing pressure. In the case of increasing temperature, gas particles gain sufficient energy to escape the solvent and solubility decreases.

The principle of solubility states that ‘like dissolves like’. Following this, it is seen that 3-Aminopropan-1-ol is a highly polar compound since it bears an amine group as well as a hydroxyl group. The polarity of amine group is due to the highly electronegative nature of N atom in N – H and C – N bonds. Since water is the most polar solvent amongst the four, it will dissolve the solute to greatest extent.

PMMA is a polymer of methyl methacrylate. It is used in the manufacturing of lenses, dentures, aircrafts windows, etc. It is known by the commercial names plexiglass, lucite, acrylite, perspex and crylux. Vectran is an aromatic polyester.

Urea formaldehyde is a thermosetting resin polymer produced by the condensation of urea and methanal. It is used in making unbreakable cups and laminated sheets.

Nomex is a highly fire-resistant meta-aramid polymer that is rigid and durable. Its monomers are m-phenylenediamine and isophthaloyl chloride. It is commonly used in firefighting equipment and in the driving apparel of racers to protect them in the case of a fire.

Glyptal is a copolymer of ethylene glycol and phthalic acid. It is an important component in the manufacturing of paints, lacquers and building materials.