General Chemistry

Question

How many grams of K₂Cr₂O₇ must be added to a 123.8 mL volumetric flask to prepare a 0.307 M K₂Cr₂O₇ solution?

Answer 1

0.307 M K₂Cr₂O₇ means 0.307 moles K₂Cr₂O₇ per liter of solution.

Since we have only 0.1238 liters of solution (123.8 mls), we will need less than 0.307 mols.

The molar mass of K₂Cr₂O₇ = 294 g / mol

0.307 mol / L x 0.1238 L = 0.0380 moles needed

0.0380 moles x 294 g / mol = 11.2 g K₂Cr₂O₇ needed (3 sig. figs.)