A 1.875 g sample of pyrazine was dissolved in 25.00g of water, producing a solution that freezes at -1.55 C. Assume the solution behaves ideally. Kf(H2O)=1.86 C/molality.

Question

A 1.875 g sample of pyrazine was dissolved in 25.00g of water, producing a solution that freezes at -1.55 C. Assume the solution behaves ideally. Kf(H2O)=1.86 C/molality.
What is the experimental molecular weight of pyrazine?

DrBob222 · Answer

delta T = Kf*molality Solve for molality molality = moles/kg solvent Solve for moles moles = grams/molecular weight Solve for molecular weight.