Class 12 Chemistry Chapter 1 Solution

Key Concept: State of Components

c) Gas
[Solution Description] In a gaseous solution where chloroform is mixed with nitrogen gas, the solvent is nitrogen because it is the component present in the largest amount. Therefore, the physical state of the solvent is gas.

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Key Concept: Complex Solution Analysis, Advanced Concentration Calculation

c) 20%
[Solution Description] The mass percentage concentration of a solute in a solution is calculated as the mass of the solute divided by the total mass of the solution, multiplied by 100. Here we need to find the mass of the solution first.

Total mass of solution = Mass of solute + Mass of solvent = 20,g + 80,g = 100,g

Now apply the formula for mass percentage:

$\text{{Mass Percentage}} = \left( \frac{{\text{{mass of solute}}}}{{\text{{total mass of solution}}}} \right) \times 100$

$\text{{Mass Percentage}} = \left( \frac{20}{100} \right) \times 100 = 20%$

Therefore, the mass percentage concentration of the solute is 20%.

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Key Concept: Concentration Units

b) 10%
[Solution Description]
To find the mass percentage, we use the formula:

Mass percentage = $$\left( \frac{\text{mass of solute}}{\text{mass of solute} + \text{mass of solvent}} \right) \times 100$$

Here, the mass of solute (salt) is 10 grams, and the mass of solvent (water) is 90 grams.

So, the mass percentage = $$\left( \frac{10}{10 + 90} \right) \times 100$$

= $$\left(\frac{10}{100}\right) \times 100$$ = 10%

The correct answer is {10%}.

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Key Concept: Dynamic Equilibrium

d) The rate of dissolution equals the rate of crystallization.
[Solution Description] In a saturated solution at dynamic equilibrium, the rate of dissolution of the solute equals the rate of crystallization. This means that while individual molecules might be moving between phases, the overall concentration of the solute remains constant.

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Key Concept: Dynamic Equilibrium, Temperature and KH

b) More $NH_3$ escapes into the vapor phase
[Solution Description] Increasing the temperature generally decreases the solubility of gases in liquids due to an endothermic dissolution process. Hence, more gas is likely to escape from the solution into the vapor phase. As per Le Chatelier’s principle, increasing temperature will cause the equilibrium position to shift so as to favor the process that absorbs heat, thus leading to an increase in ammonia gas concentration in the vapor phase.

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Key Concept: Van’t Hoff Factor

a) 1
[Solution Description] The depression in freezing point $(\Delta T_f)$ is given by the formula $\Delta T_f = i \cdot K_f \cdot m$, where $i$ is the Van’t Hoff factor, $K_f$ is the cryoscopic constant, and $m$ is the molality of the solution.

Rearrange the formula to solve for $i$:
$$i = \frac{\Delta T_f}{K_f \cdot m}$$

Given:
$$\Delta T_f = 0.372 \text{ K}$$
$$K_f = 1.86 \text{ K kg/mol}$$
$$m = 0.2 \text{ mol/kg}$$

Substitute these values into the equation:
$$
i = \frac{0.372}{1.86 \times 0.2} = \frac{0.372}{0.372} = 1
$$
Therefore, the Van’t Hoff factor for the salt is 1.

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Key Concept: Complex Solubility, Advanced Equilibrium

d) Solubility increases due to lowered temperature favoring exothermic process
[Solution Description] The dissolution of nitrogen in palladium being an exothermic process means that heat is released when the nitrogen dissolves. According to Le Chatelier’s principle, if the temperature decreases, the system will shift to favor the exothermic process, which increases the solubility of nitrogen. Therefore, cooling the system would increase solubility.

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Key Concept: Molarity Calculation

b) 1.0 M
[Solution Description] Molarity (M) is defined as the number of moles of solute per liter of solution. The formula to calculate molarity is $$M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}$$.

First, calculate the number of moles of glucose:

$$
\text{Moles of } C_6H_{12}O_6 = \frac{\text{mass}}{\text{molar mass}} = \frac{180 \, \text{g}}{180 \, \text{g/mol}} = 1 \text{ mole}
$$

Since the volume of the solution is 1 L, the molarity is:

$$
M = \frac{1 \, \text{mol}}{1 \, \text{L}} = 1 \, \text{M}
$$

Thus, the molarity of the glucose solution is 1 M.

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Key Concept: Solvent Identification

b) Water
[Solution Description] In the given solution, water is present in a larger quantity than the salt, hence water is the solvent based on the definition that the solvent is the component in the largest quantity.

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Key Concept: Application in Industry

a) It remains constant under varying temperatures, ensuring process consistency.
[Solution Description] Mass percentage is frequently used in industry because it provides an easy way to express concentrations that remain consistent regardless of temperature fluctuations. This makes it suitable for large-scale processes where precise measurements and consistency over varying conditions are critical.

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