Question

63g of a compound (Mol.Wt.=126) was dissolved in 500g of distilled water.The density of the resultant solution is 1.126g/ml. The molarity of the solution is

• A. 1.25M
• B. 1.0M
• C. 0.75M
• D. 1.1M

Answer 1

Answer: (B)

1.0M

Answer 2

To find the molarity of the solution, we first need to calculate the number of moles of the compound and then use the formula for molarity.
Given:
- Mass of compound = 63 g
- Molecular weight of compound = 126 g/mol
- Mass of water = 500 g
- Density of solution = 1.126 g/ml
First, let's find the volume of the solution. The density formula is $\text{density} = \frac{\text{mass}}{\text{volume}}$, so the volume of the solution is:
$\text{Volume of solution} = \frac{\text{mass of solution}}{\text{density of solution}} = \frac{63 g + 500 g}{1.126 g/ml}$
$\text{Volume of solution} = \frac{563 g}{1.126 g/ml}$
$\text{Volume of solution} = 500 ml$
Since the density of water is 1 g/ml, the mass of water in the solution is 500 g. This means the mass of the compound in the solution is $63 \text{ g}$. Since the compound's molecular weight is 126 g/mol, the number of moles of the compound in the solution is:
$\text{Moles of compound} = \frac{\text{Mass of compound}}{\text{Molecular weight of compound}}$
$\text{Moles of compound} = \frac{63 \text{ g}}{126 \text{ g/mol}}$
$\text{Moles of compound} = 0.5 \text{ mol}$
Now, the molarity of the solution is given by the formula:
$\text{Molarity} = \frac{\text{Moles of solute}}{\text{Volume of solution in liters}}$
Since we have 0.5 moles of compound and the volume of the solution is 500 ml (0.5 liters), the molarity is:
$\text{Molarity} = \frac{0.5 \text{ mol}}{0.5 \text{ L}}$
$\text{Molarity} = 1.0 \text{ M}$
Therefore, the molarity of the solution is 1.0 M.
The correct answer is option (B): 1.0M