Question

The following solutions were prepared by dissolving 1 g of solute in 1 L of the solution. Arrange the following solutions in decreasing order of their molarity: (A) Glucose (molar mass = 180 g mol$^{-1}$)
(B) NaOH (molar mass = 40 g mol$^{-1}$)
(C) NaCl (molar mass = 58.5 g mol$^{-1}$)
(D) KCl (molar mass = 7(4)5 g mol$^{-1}$)

• A. (A), (D), (C), (B)
• B. (A), (B), (C), (D)
• C. (B), (C), (D), (A)
• D. (D), (C), (A), (B)

Hint:

When comparing the molarity of solutions, focus on the molar mass of the solute. A lower molar mass results in higher molarity when the same mass of solute is used.

Answer 1

The Correct Option is A

Step 1: Molarity Formula.
Molarity (M) is calculated using the formula: \[M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}\]Given 1 g of solute per 1 L of solution, molarity is numerically equivalent to the moles of solute.
Step 2: Moles Calculation.
The number of moles is determined by: \[\text{moles of solute} = \frac{\text{mass of solute}}{\text{molar mass of solute}}\]Calculating moles for each solute:
- Glucose (A): \[ \text{moles of glucose} = \frac{1 \, \text{g}}{180 \, \text{g/mol}} = 0.00556 \, \text{mol} \] Molarity of glucose: \[ M = 0.00556 \, \text{mol/L} \]- NaOH (B): \[ \text{moles of NaOH} = \frac{1 \, \text{g}}{40 \, \text{g/mol}} = 0.025 \, \text{mol} \] Molarity of NaOH: \[ M = 0.025 \, \text{mol/L} \]- NaCl (C): \[ \text{moles of NaCl} = \frac{1 \, \text{g}}{58.5 \, \text{g/mol}} = 0.01709 \, \text{mol} \] Molarity of NaCl: \[ M = 0.01709 \, \text{mol/L} \]- KCl (D): \[ \text{moles of KCl} = \frac{1 \, \text{g}}{74.5 \, \text{g/mol}} = 0.01342 \, \text{mol} \] Molarity of KCl: \[ M = 0.01342 \, \text{mol/L} \]Step 3: Order by Molarity.
Arranging the molarities in decreasing order:
1. NaOH (B): 0.025 mol/L (Highest)
2. NaCl (C): 0.01709 mol/L
3. KCl (D): 0.01342 mol/L
4. Glucose (A): 0.00556 mol/L (Lowest)
The correct sequence is: (B), (C), (D), (A).
Final Answer: \[\boxed{\text{The correct sequence is (B), (C), (D), (A).}}\]