Physical Chemistry

Molarity $M = \frac{\text{Mass of solute}}{\text{Molar mass} \times V\text{ (in L)}} = \frac{1}{M_w \times 1} = \frac{1}{M_w}$.
For a fixed mass of $1\text{ g}$ in $1\text{ L}$, molarity is inversely proportional to molar mass:

• $\text{NaOH}$: $M_w = 40 \implies M = 1/40 = 0.025\text{ M}$ (highest molarity)
• $\text{NaCl}$: $M_w = 58.5 \implies M = 1/58.5 \approx 0.017\text{ M}$
• $\text{KCl}$: $M_w = 74.5 \implies M = 1/74.5 \approx 0.013\text{ M}$
• Glucose: $M_w = 180 \implies M = 1/180 \approx 0.0055\text{ M}$ (lowest molarity)
  Decreasing order of molarity: (B) > (C) > (D) > (A).

Definitions of solutions and osmotic properties:

• Saturated solution: Contains the maximum amount of solute that can dissolve in a solvent at a given temperature $\rightarrow$ (III)
• Isotonic solutions: Two solutions possessing the exact same osmotic pressure at a given temperature $\rightarrow$ (IV)
• Binary solution: A homogeneous mixture containing exactly two chemical components (solute and solvent) $\rightarrow$ (I)
• Hypertonic solution: A solution with higher osmotic pressure relative to another solution $\rightarrow$ (II)
  Correct match: (A)-(III), (B)-(IV), (C)-(I), (D)-(II).

According to Henry's law, the solubility of a gas in a liquid is directly proportional to its partial pressure above the liquid. At high altitudes, atmospheric pressure is considerably lower than at sea level, leading to a reduced partial pressure of oxygen. Consequently, less oxygen dissolves in the blood and tissues, causing weakness and mental fatigue (anoxia).

In $100\text{ g}$ of $20\%\text{ (w/w)}$ solution:

• Mass of $\text{KI}$ (solute) $= 20\text{ g}$
• Mass of water (solvent) $= 100 - 20 = 80\text{ g} = 0.080\text{ kg}$
• Moles of $\text{KI} = \frac{20\text{ g}}{166\text{ g mol}^{-1}} \approx 0.1205\text{ mol}$
  $$\text{Molality } m = \frac{\text{Moles of solute}}{\text{Mass of solvent (kg)}} = \frac{0.1205}{0.080} \approx 1.506\text{ mol kg}^{-1} \approx 1.5\text{ mol kg}^{-1}$$