Question

What is the molarity of a solution prepared by dissolving 12.0 g of caffeine, c8h10n4o2, in water and diluting it to 250.0 ml?

Answer 1

Answer: 0.247 M

Explanation:


1) Data:

solute: C₈H₁₀N₄O₂
mass of solute: 12.0 g

Volume of solution: 250.0 ml = 0.2500 liter

M = ?



2) Formulas:

M = number of moles of solute / number of liters of solution
number of moles of solute = mass in grams / molar mass

3) Solution:

i) molar mass of C₈H₁₀N₄O₂: 8×12.011 g/mol + 10×1.008 g/mol + 4×14.007g/mol + 2×15.999 g/mol = 194.194 g/mol

ii) number of moles of solute = 12.0 g / 194.194 g/mol = 0.06179 moles

iii) molarity

M = 0.06179 / 0.250 liter = 0.247 moles / liter