Question

A mass of 100.0 g of solute is dissolved in water so that 850. mL of a 0.7500 M solution has been prepared. What is the molar mass of the solute?

Answer 1

Answer:

156.86 g / mol

Explanation:

We start from the molarity law  

Cm = n / V

n = w / M

then

Cm = (w / M) / V

Cm = w / (M × V)

where:

Cm is the molarity  

n number of moles

w a mass of the solute  

M is the molar mass of the solute (which is needed)

V the volume of the solution in liters

Then the M can be calculated as following:  

M = w / (Cm × V)

M = 100 / (0.75 × 0.85) = 156.86 g / mol