Question

4.5 g of compound A (MW = 90) was used to make 250 mL of its aqueous solution. The molarity of the solution in M is $x \times 10^{-1}$. The value of $x$ is __________. (Rounded off to the nearest integer)

Hint:

Molarity is defined as moles of solute per liter of solution. Always ensure volume is in Liters (L) before dividing.

Answer 1

Correct Answer: 2

Step 1: Calculate the number of moles of compound A: $n = \frac{\text{mass}}{\text{molar mass}} = \frac{4.5}{90} = 0.05$ mol.
Step 2: Convert volume to liters: $V = 250 \text{ mL} = 0.25$ L.
Step 3: Calculate molarity: $M = \frac{n}{V} = \frac{0.05}{0.25} = 0.2$ M.
Step 4: Express in required form: $0.2 = 2 \times 10^{-1}$.
Step 5: Therefore, $x = 2$.