Question

The molarity of a 70%(mass/mass) aqueous solution of a monobasic acid (X) is:

Answer 1

Correct Answer: 12.5

To determine the molarity of the solution, execute the following steps:

1. Solute Mass in 100g of Solution:
A 70% (mass/mass) solution indicates 70g of acid (X) per 100g of solution.

2. Volume of 100g Solution:
Utilize the density formula:

$ \text{Density} = \frac{\text{Mass}}{\text{Volume}} $
Rearrange to solve for volume:

$ \text{Volume} = \frac{\text{Mass}}{\text{Density}} $

Input the given values:

$ \text{Volume} = \frac{100 \, \text{g}}{1.25 \, \text{g/mL}} = 80 \, \text{mL} = 0.080 \, \text{L} $

3. Moles of Solute:
Calculate moles using the formula:

$ \text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} $

Substitute the values:

$ \text{Moles} = \frac{70 \, \text{g}}{70 \, \text{g/mol}} = 1 \, \text{mol} $

4. Molarity Calculation:
Molarity is defined as moles of solute per liter of solution:

$ \text{Molarity} = \frac{\text{Moles of Solute}}{\text{Volume of Solution (in liters)}} $

Input the calculated values:

$ \text{Molarity} = \frac{1 \, \text{mol}}{0.080 \, \text{L}} = 12.5 \, \text{M} $

Conclusion:
The solution's molarity is $ 12.5 $.