Question

If 18 g of glucose is dissolved in 1000 g of solvent, then the solution is said to be:

• A. 1 molar
• B. 0.1 molal
• C. 0.1 molar
• D. 0.5 molal

Hint:

Molality depends only on solvent mass, while molarity depends on total solution volume and varies with temperature.

Answer 1

The Correct Option is B

Step 1: Calculate moles of solute.
Molecular mass of glucose = 180 g/mol.
Moles of glucose = \(\frac{18}{180} = 0.1\) mol.
Step 2: Define molality.
Molality = (moles of solute) / (mass of solvent in kg).
Here solvent = 1000 g = 1 kg.
\[ \text{Molality} = \frac{0.1}{1} = 0.1 \, \text{molal} \] Step 3: Analyze options.
- 1 molar: Wrong (molarity depends on solution volume, not mass of solvent).
- 0.1 molal: Correct.
- 0.1 molar: Incorrect because molarity ≠ molality here.
- 0.5 molal: Wrong, calculation mismatch.
Step 4: Conclusion.
Thus, the solution is 0.1 molal.