Solutions

According to Henry’s Law, in gases, an increase in pressure increases:

• Option 1: Solubility - This is the correct answer. Henry's Law states that the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. When the pressure increases, more gas dissolves into the liquid.
• Option 2: Saturation - While increasing pressure can lead to a more saturated solution, Henry’s Law specifically deals with the solubility of gases, not saturation.
• Option 3: Volume - This is incorrect because the volume of a gas decreases with an increase in pressure (according to Boyle’s Law), not its solubility.
• Option 4: Viscosity - This is unrelated to Henry’s Law. Viscosity is the measure of a liquid’s resistance to flow, and it does not directly relate to pressure in the context of Henry’s Law.

Explanation:

Henry’s Law states that for a gas dissolved in a liquid at a constant temperature, the amount of gas that dissolves is directly proportional to the partial pressure of the gas above the liquid. So, as the pressure of the gas increases, the solubility of the gas in the liquid also increases.

The saturation temperature for 20.7g of CuSO4 soluble in water is:

• Option 1: 100°C - This is the correct answer. Copper sulfate (CuSO4) is known to be highly soluble in water, and at standard conditions, it dissolves in water at temperatures around 100°C. This is a typical saturation temperature for such solutes.
• Option 2: 1000°C - This is much too high and not the correct answer. Copper sulfate does not require such high temperatures to reach saturation.
• Option 3: 200°C - This temperature is still too high for the saturation of CuSO4 in water, making it an incorrect option.
• Option 4: 300°C - This is also not the correct saturation temperature for copper sulfate in water.

Explanation:

The saturation temperature refers to the temperature at which a given amount of solute (in this case, CuSO4) will dissolve completely in a solvent (water). For CuSO4, around 100°C is the typical saturation temperature, where the solute reaches its maximum solubility in water under normal conditions.

The solution in which saturation is not achieved is called:

• Option 1: Super saturated - This refers to a solution that holds more solute than it can normally dissolve at a given temperature. It is a state of saturation, but in excess.
• Option 2: Unsaturated - This is the correct answer. An unsaturated solution is one in which the solvent can still dissolve more solute. Saturation has not been achieved yet.
• Option 3: Saturated - A saturated solution is one in which the solvent has dissolved the maximum amount of solute possible at a given temperature and pressure.
• Option 4: Suspended - A suspended solution is one where solid particles are temporarily dispersed in the solvent but have not dissolved.

Explanation:

An unsaturated solution occurs when the solute has not reached the point of saturation, meaning more solute can still dissolve in the solvent. This is the state before reaching a saturated solution.

Aqueous Solutions and Solvent

An aqueous solution is a solution where the solvent is water. In such solutions, the solute is dissolved in water.

Understanding Aqueous Solutions

In an aqueous solution, the term "aqueous" specifically refers to water being the solvent. This is a key concept in chemistry because water is one of the most common solvents used to dissolve substances, especially ionic compounds.

Why Water is the Solvent

Water is used as a solvent in aqueous solutions due to its unique properties:

• Polarity: Water is a polar molecule, meaning it has a partial positive charge on one side and a partial negative charge on the other. This allows it to dissolve many ionic and polar substances.
• High Solubility: Water can dissolve a wide range of substances, including salts, acids, and gases, making it an excellent solvent for many chemical reactions.
• Ability to form hydrogen bonds: Water molecules can form hydrogen bonds with various solutes, enhancing the dissolving process.

Common Examples of Aqueous Solutions

Some examples of aqueous solutions include:

• Sodium chloride (NaCl) in water, commonly known as saltwater.
• Hydrochloric acid (HCl) in water, forming a strong acid solution.
• Sugar (C₆H₁₂O₆) dissolved in water to make a sweet solution.

Other Solvents and Their Roles

While water is the most common solvent for aqueous solutions, other solvents like benzene, ether, and alcohol are used in different types of solutions:

• Benzene: A non-polar solvent used in organic chemistry, but not in aqueous solutions.
• Ether: Another organic solvent used for dissolving non-polar substances, but not suitable for aqueous solutions.
• Alcohol: Commonly used as a solvent in both organic and aqueous solutions, depending on the substance being dissolved.

Conclusion

In summary, the solvent used in aqueous solutions is water, which provides an ideal environment for dissolving many substances due to its polarity, high solubility, and hydrogen bonding ability.

In the context of chemistry, a true solution is a homogeneous mixture where the solute particles are completely dissolved in the solvent. The size of these particles determines the category into which the solution falls.

The particle size of the solute in a true solution typically falls within a specific range:

• 1 Å–10 Å (angstroms)

This size range of solute particles ensures they are completely dissolved in the solvent, making the mixture homogeneous at the molecular level. Therefore, the correct option is: 1 Å – 10 Å.

• Water: This is used to prepare aqueous solutions, as it is the solvent in such solutions.
• Kerosene: This is a hydrocarbon and is not used in aqueous solutions as a solvent.
• Petrol: Like kerosene, petrol is also a hydrocarbon and not used in aqueous solutions.

Solutions are categorized into aqueous and non-aqueous solutions based on the nature of the solvent. In chemistry:

• Aqueous solutions involve water as the solvent. Water's unique properties make it a universal solvent, capable of dissolving a wide range of substances.
• Non-aqueous solutions, on the other hand, involve solvents other than water. These solvents can dissolve substances that are not soluble in water and are crucial in processes where water's properties are unsuitable.

Understanding the nature of the solvent is essential to determine the type of solution, as it directly influences the solution’s properties such as solubility, conductivity, and reactivity.

• Option 1: Brownian motion - This is incorrect. Brownian motion refers to the random movement of colloidal particles suspended in a medium, not the scattering of light.
• Option 2: Tyndall effect - This is the correct answer. The Tyndall effect refers to the scattering of light by colloidal particles or small particles in a medium. This is what makes the path of light visible when dust particles scatter sunlight.
• Option 3: Raman effect - The Raman effect refers to the scattering of light in which there is a shift in the wavelength of light due to interactions with molecules. This is not the phenomenon described here.
• Option 4: Uniform motion - This is incorrect. Uniform motion refers to motion at a constant speed in a straight line, which does not relate to the scattering of light.

Explanation:

The phenomenon described is called the Tyndall effect. It occurs when light is scattered by small particles or colloidal particles, making the path of light visible. In the case of sunlight passing through a window, dust particles scatter the light, which is why we can see the beam of light.

• Option 1: Hess’ law - Hess' law relates to the heat changes in chemical reactions, not to the solubility of solvents. Therefore, this is not the correct answer.
• Option 2: Henry’s law - This is the correct answer. Henry’s Law states that the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid, provided the temperature is constant.
• Option 3: Charles’ Law - Charles' Law relates to the relationship between the volume and temperature of a gas, not the solubility of solvents. Therefore, this is not the correct answer.
• Option 4: Boyle’s law - Boyle’s law describes the relationship between the pressure and volume of a gas at constant temperature, but it does not describe the solubility of solvents. Hence, this is not the correct answer.

Explanation:

Henry's Law is the correct law that describes the relationship between the solubility of gases in solvents and pressure. According to Henry’s Law, the solubility of a gas increases as the pressure of the gas above the solvent increases, assuming temperature remains constant.

On increasing the temperature, the solubility of the solute in the solvent:

• Option 1: Increase - This is the correct answer. In most cases, increasing the temperature increases the solubility of solid solutes in a liquid. This is because higher temperatures provide more energy for the solute particles to dissolve.
• Option 2: Decrease - This is incorrect. For most solid solutes, solubility increases with temperature. However, for gases, solubility tends to decrease with an increase in temperature.
• Option 3: Change - This is too vague. The solubility of a solute typically either increases or decreases with temperature, depending on the nature of the solute and solvent.
• Option 4: Does not change - This is incorrect. Solubility does change with temperature for most substances, especially for solids in liquids.

Explanation:

For most solid solutes in liquids, increasing the temperature increases solubility. This happens because higher temperatures provide more kinetic energy to the solute particles, making it easier for them to dissolve. However, for gases, solubility decreases as temperature increases.

Deep sea divers use a mixture of:

• Option 1: Helium - Oxygen - This is the correct answer. Deep sea divers often use a mixture of helium and oxygen, known as heliox, to avoid nitrogen narcosis and to reduce the risk of decompression sickness at great depths.
• Option 2: Nitrogen - Oxygen - This is commonly used in regular air for diving, but at greater depths, it can cause nitrogen narcosis. This is not the best option for deep sea divers.
• Option 3: Hydrogen - Nitrogen - This is not typically used in diving, as hydrogen is highly flammable and would pose significant risks to divers.
• Option 4: Helium - Nitrogen - This is not a typical gas mixture for deep sea diving. Helium is usually mixed with oxygen, not nitrogen, for deep diving.

Explanation:

Deep sea divers use a mixture of helium and oxygen (heliox) to prevent the risks associated with using air at extreme depths, such as nitrogen narcosis and oxygen toxicity. Helium is an inert gas and does not cause narcosis, making it safer for deep diving.

Solubility of CaO in water is:

• Option 1: Chermic - This is not a correct term related to solubility or dissolution processes. It appears to be a typographical error.
• Option 2: Endothermic - This is incorrect. An endothermic process absorbs heat, but the dissolution of CaO in water releases heat.
• Option 3: Exothermic - This is the correct answer. When calcium oxide (CaO) dissolves in water, it reacts exothermically, releasing a significant amount of heat and forming calcium hydroxide (Ca(OH)2).
• Option 4: Hypothermic - This is not a recognized term in chemistry related to the dissolution process.

Explanation:

The dissolution of calcium oxide (CaO) in water is an exothermic process, meaning that it releases heat. The reaction produces calcium hydroxide (Ca(OH)2) and is highly exothermic, making it feel hot to the touch.

The increase in the solubility of Sodium halides, in water at 25°C is:

• Option 1: NaCl > NaBr > NaI - This is incorrect. As the size of the halide ion increases, the solubility tends to decrease.
• Option 2: NaBr > NaI > NaCl - This is also incorrect. The solubility does not follow this trend at 25°C.
• Option 3: NaI > NaBr > NaCl - This is the correct answer. The solubility of sodium halides in water increases as the size of the halide ion increases. NaI has the highest solubility, followed by NaBr, and NaCl has the lowest solubility.
• Option 4: NaCl = NaBr > NaI - This is incorrect because NaI has a higher solubility than both NaCl and NaBr at 25°C.

Explanation:

The solubility of sodium halides in water at 25°C increases in the order of NaI > NaBr > NaCl. This is because as the ionic radius of the halide ion increases, the lattice energy of the salt decreases, allowing it to dissolve more easily in water.

The solubility level of an aqueous solution of NaCl at 25°C is:

• Option 1: 20g - This is lower than the actual solubility of NaCl at 25°C.
• Option 2: 36g - This is the correct answer. Sodium chloride (NaCl) has a solubility of approximately 36 grams in 100 milliliters of water at 25°C.
• Option 3: 95g - This is too high for the solubility of NaCl at 25°C. NaCl does not dissolve at this high concentration in water at this temperature.
• Option 4: 8g - This is far too low for the solubility of NaCl in water at 25°C.

Explanation:

The solubility of NaCl (sodium chloride) in water at 25°C is approximately 36g per 100mL of water. This is the correct answer as it reflects the typical solubility of NaCl under normal conditions at this temperature.