Chapter 1: Solutions Application Questions | chemistry Class 12 CBSE

ByteNotes

Chapter 1: Solutions Application Questions | chemistry Class 12 CBSE | ByteNotes.in

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 1

Applied Concept

A diver breathing compressed air at a depth of 30 metres suddenly ascends rapidly to the surface. He experiences severe joint pain and breathing difficulties. With reference to Henry's law, explain what has happened and suggest how this could have been prevented.

At 30 m depth, the water pressure is much higher than atmospheric pressure; by Henry's law (p = KH × x), increased partial pressure of N2 increases its solubility in blood, dissolving large quantities of nitrogen.
Rapid ascent causes sudden pressure drop; the dissolved nitrogen, now supersaturated, comes out rapidly as gas bubbles in blood and joints. These bubbles block capillaries, causing the painful, life-threatening 'bends' (decompression sickness).
Prevention: the diver should ascend slowly, allowing gradual decompression so nitrogen leaves the blood slowly; scuba tanks should be filled with helium-diluted air (11.7% He, 56.2% N2, 32.1% O2) since helium has much higher KH and is far less soluble in blood.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

In hilly regions, water boils at temperatures below 100°C, making cooking difficult. A cook adds salt to the cooking water. With reference to the colligative properties of solutions, explain why this helps in cooking food more effectively.

At high altitudes, atmospheric pressure is lower; water boils at a temperature below 100°C (e.g., at about 95°C on some hills) since vapour pressure equals the lower atmospheric pressure at a lower temperature, providing less heat for cooking.
When salt (NaCl) is added to water, it dissolves and elevates the boiling point: ΔTb = i Kb m. Salt dissociates into Na⁺ and Cl⁻ (i ≈ 2), effectively doubling the molal concentration for the same mass, raising the boiling point further.
A higher boiling point means food cooks at a higher temperature, reducing cooking time and ensuring food is properly cooked despite the lower atmospheric pressure. This is a direct application of elevation of boiling point as a colligative property.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 3

Applied Concept

A sample of drinking water from a village was tested and found to contain fluoride ion concentration of 1.0 ppm. Another source showed 2.0 ppm of fluoride ions. With reference to the chapter, comment on the safety of each source for drinking.

Fluoride concentration is expressed in ppm (parts per million) — the chapter mentions that 1 ppm of fluoride ions in water prevents tooth decay and is considered safe for drinking.
A concentration of 1.0 ppm is within the beneficial and safe range described in the chapter; it can help prevent dental cavities and is suitable for drinking.
A concentration of 2.0 ppm exceeds the threshold of 1.5 ppm stated in the chapter (above which teeth become mottled); at higher concentrations, fluoride can be poisonous (e.g., NaF is used in rat poison). Therefore, 2.0 ppm is unsafe for regular consumption and treatment or an alternative source is needed.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 4

Applied Concept

An antifreeze solution containing 35% (v/v) ethylene glycol is used in the cooling system of a car in a cold region. Explain the principle behind its use, identifying which colligative property is relevant.

Ethylene glycol (C2H6O2) is a non-volatile solute; when dissolved in water in the car radiator, it depresses the freezing point of water: ΔTf = Kf × m.
The 35% (v/v) ethylene glycol solution lowers the freezing point of water to about 255.4 K (−17.6°C) as stated in the chapter, preventing the coolant from freezing in cold weather, which would otherwise damage the radiator and engine block.
This is a practical application of depression of freezing point (a colligative property); the amount of depression depends on the number of solute particles (molality), not on the chemical identity of the solute.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 5

Applied Concept

A patient requires an intravenous saline injection. The hospital uses a 0.9% (mass/volume) NaCl solution. Explain why this specific concentration is chosen and what would happen if a 2% NaCl solution were used instead.

The 0.9% (mass/volume) NaCl solution is isotonic with blood plasma — it has the same osmotic pressure as the fluid inside blood cells. When injected intravenously, no osmosis occurs across the red blood cell membranes, so cells maintain their normal shape and function.
If a 2% NaCl solution (hypertonic) were used, it would have a higher osmotic pressure than the cell interior. Water would flow out of the blood cells by osmosis, causing the cells to shrink and collapse (crenation), potentially leading to serious medical complications.
This illustrates the critical importance of osmotic pressure as a colligative property in medical applications; isotonic solutions ensure that cells are neither swollen by hypotonic nor shrunken by hypertonic conditions.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 6

Applied Concept

In a laboratory, a student finds that 18 g of glucose dissolved in 1 kg of water boils at 373.202 K. Using this information, verify whether glucose behaves as a normal (non-electrolyte) solute in this experiment.

Moles of glucose (M = 180 g mol⁻¹) = 18/180 = 0.1 mol; molality = 0.1 mol/1 kg = 0.1 mol kg⁻¹.
Using ΔTb = Kb × m = 0.52 K kg mol⁻¹ × 0.1 mol kg⁻¹ = 0.052 K; expected boiling point = 373.15 + 0.052 = 373.202 K.
The observed boiling point (373.202 K) exactly matches the calculated value, confirming that glucose does not dissociate or associate in aqueous solution; van't Hoff factor i = 1. Glucose behaves as a normal, non-electrolyte, non-associating solute.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 7

Applied Concept

A packet of potato chips is inflated with nitrogen gas and sealed at sea level, but appears puffed up when taken to a hill station at high altitude. Explain this observation.

The packet is sealed at sea level where atmospheric pressure is higher (~1 atm); the nitrogen gas inside is compressed to a certain volume under this external pressure.
At high altitude, the atmospheric pressure is significantly lower than at sea level; the external pressure acting on the packet decreases.
Since the nitrogen inside remains at a pressure close to 1 atm (or slightly above), the reduced external pressure means the internal gas now pushes outward more strongly, causing the packet to expand and appear more inflated or puffed up. This is related to the pressure dependence of gas behaviour.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 8

Applied Concept

When pickles are prepared by immersing raw mangoes in concentrated brine (salt solution), the mangoes shrivel over time. Explain this phenomenon using the concept of osmosis.

Concentrated brine has a very high solute (NaCl) concentration and therefore a very high osmotic pressure compared to the fluid inside the cells of raw mangoes.
The cell walls of mango act as semipermeable membranes; by the process of osmosis, water flows from inside the mango cells (region of lower solute concentration) through the cell membrane to the concentrated brine (region of higher solute concentration).
As water leaves the mango cells, they lose turgor pressure and the cells collapse; the overall mango shrinks and shrivels. This is a practical application of osmosis and is the principle behind preservation of food by salting — the bacterium on the salted surface also loses water and dies, preventing spoilage.

ByteNotes

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 9

Applied Concept

In preparing a soft drink, CO2 is dissolved in water under high pressure and the bottle is sealed. Explain, using Henry's law, what happens when the bottle cap is opened, and why the drink goes flat if left open.

According to Henry's law, the solubility of CO2 in water is directly proportional to its partial pressure: p = KH × x. High pressure during bottling forces large amounts of CO2 to dissolve in the liquid (high mole fraction of CO2 in solution).
When the bottle cap is opened, the pressure above the liquid suddenly drops to atmospheric pressure. Since the partial pressure of CO2 decreases, the dissolved CO2 is now supersaturated; the equilibrium shifts to release CO2, which escapes as bubbles — the characteristic fizzing.
If the open bottle is left for some time, CO2 continues to escape until the solution reaches equilibrium with the atmospheric partial pressure of CO2 (which is very low, ~0.0003 atm); at this low pressure, very little CO2 remains dissolved and the drink loses its carbonation — it goes flat.

ByteNotes

Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 10

Applied Concept

A student performs an experiment to determine the molar mass of an unknown protein. She dissolves 1.26 g of the protein in 200 mL of water and measures the osmotic pressure at 300 K as 2.57 × 10⁻³ bar. Calculate the molar mass and explain why osmotic pressure was chosen over other colligative methods.

Using Π = (w2RT)/(M2V): M2 = w2RT/(ΠV) = (1.26 g × 0.083 L bar K⁻¹ mol⁻¹ × 300 K) / (2.57 × 10⁻³ bar × 0.200 L) = 31.374 / 5.14 × 10⁻⁴ ≈ 61,022 g mol⁻¹.
Osmotic pressure was chosen because even the very small concentration of this large protein generates a measurable osmotic pressure; other methods like boiling point elevation (Kb = 0.52 for water) would give ΔTb too small to measure accurately (of the order of 10⁻⁵ K).
Additionally, the protein is thermally unstable at higher temperatures required for boiling point elevation; osmotic pressure measurements are conducted at near room temperature (300 K) preserving the protein's structure, making it the ideal method for biomolecule molar mass determination.

ByteNotes

Premium Access

Unlock all Application Questions

You are viewing 10 free application questions from this chapter. Upgrade to Premium to unlock the remaining 12 questions.

Upgrade to Premium12 questions locked

Chapter sections

Chapter 1: Solutions | Application Questions

A diver breathing compressed air at a depth of 30 metres suddenly ascends rapidly to the surface. He experiences severe joint pain and breathing difficulties. With reference to Henry's law, explain what has happened and suggest how this could have been prevented.

In hilly regions, water boils at temperatures below 100°C, making cooking difficult. A cook adds salt to the cooking water. With reference to the colligative properties of solutions, explain why this helps in cooking food more effectively.

A sample of drinking water from a village was tested and found to contain fluoride ion concentration of 1.0 ppm. Another source showed 2.0 ppm of fluoride ions. With reference to the chapter, comment on the safety of each source for drinking.

An antifreeze solution containing 35% (v/v) ethylene glycol is used in the cooling system of a car in a cold region. Explain the principle behind its use, identifying which colligative property is relevant.

A patient requires an intravenous saline injection. The hospital uses a 0.9% (mass/volume) NaCl solution. Explain why this specific concentration is chosen and what would happen if a 2% NaCl solution were used instead.

In a laboratory, a student finds that 18 g of glucose dissolved in 1 kg of water boils at 373.202 K. Using this information, verify whether glucose behaves as a normal (non-electrolyte) solute in this experiment.

A packet of potato chips is inflated with nitrogen gas and sealed at sea level, but appears puffed up when taken to a hill station at high altitude. Explain this observation.

When pickles are prepared by immersing raw mangoes in concentrated brine (salt solution), the mangoes shrivel over time. Explain this phenomenon using the concept of osmosis.

In preparing a soft drink, CO2 is dissolved in water under high pressure and the bottle is sealed. Explain, using Henry's law, what happens when the bottle cap is opened, and why the drink goes flat if left open.

Unlock all Application Questions