Question

A student dissolves 14.g of benzoic acid C7H6O2 in 425.mL of a solvent with a density of 0.92 g/mL. The student notices that the volume of the solvent does not change when the benzoic acid dissolves in it.Calculate the molarity and molality of the student's solution. Round both of your answers to 2 significant digits.

Answer 1

Answer:

Molarity of the solution is 0.26 M and molality of the solution is 0.28 m

Explanation:

Molar mass of benzoic acid = 122.12 g/mol

So, 14. g of benzoic acid = $\frac{14.}{122.12}mol$ of benzoic acid = 0.11 mol of benzoic acid

We know, density is the ratio of mass to volume

So, mass of 425. mL of solvent  = $(425.\times 0.92)g=391 g$

Molarity is defined as number of moles of solute dissolved in 1000 mL of solution

Here solute is benzoic acid and total volume of solution is 425. mL

So, molarity of solution = $\frac{0.11}{425.}\times 1000M=0.26M$

Molality is defined as number of moles of solute dissolved in 1000 g of solvent

So, molality of solution = $\frac{0.11}{391}\times 1000m=0.28m$