Question

Calculate the mass (in grams) needed to prepare 0.574 liters of a 8.48 M caffeine solution. The formula of caffeine is C8H10N4O2. You do not need to enter units with your answer.

Answer 1

Molar mass of caffeine can be calculated from molecular formula as follows:

Molar mass of caffeine = (mass of C x 8) + (mass of H x 10) + (mass of N x 4) + (mass of O x 2)

Molar mass of caffeine = (12 x 8) + (1 x 10) + (14 x 4) + (16 x 2)

Molar mass of caffeine = 194 g/mol

Number of moles of caffeine in 0.574 liters of 8.48 M solution can be calculated as follows:

Number of moles of caffeine = Volume x molarity

Number of moles of caffeine = 0.574 L x 8.48 mol/L

Number of moles of caffeine = 4.87 mol

Therefore,

Mass of 4.87 moles of caffeine can be calculated as follows:

Mass of caffeine = moles of caffeine x molar mass of caffeine

Mass of caffeine = 4.87 mol x 194 g/mol

Mass of caffeine = 945 g

Thus, mass of caffeine needed to prepare 0.547 L of 8.48 M solution is 945 g.