A laboratory technician needs to prepare an aqueous solution of potassium nitrate for…
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A laboratory technician needs to prepare an aqueous solution of potassium nitrate for an experiment on reaction rates. A clean, dry beaker is weighed and found to have a mass of 42.63 g. After adding solid KNO₃ to the beaker, its mass is 47.63 g. The contents of the beaker are quantitatively transferred to a 250.0 mL volumetric flask, water is added to the calibration mark, and the mixture is thoroughly mixed.
Atomic masses (g mol⁻¹): K 39.10, N 14.01, O 16.00
(1) Calculate the number of moles of KNO₃ that were used to prepare the solution.
(2) Determine the molarity of the potassium nitrate solution, reporting your answer to three significant figures.
(3) Briefly comment on whether the initial mass of the empty beaker has any effect on the calculated molarity and justify your reasoning.