Answer to Question #136091 in General Chemistry for Justus Cagle

Question

A student weighs out 9.39 g of Co(NO3)2, transfers it to a 300. mL volumetric flask, adds enough water to dissolve the solid and then adds water to the 300 mL mark on the neck of the flask.

Calculate the concentration (in molarity units) of cobalt(II) nitrate in the resulting solution?

Answer 1

Solution:

Molar concentration (С) is calculated by dividing the moles of solute (n) by the total volume (V) of the:

С = n/V

We must convert the mass of Co(NO₃)₂  in grams into moles. We do this by dividing by the molecular weight of Co(NO₃)₂ (182.93 gram/mol).

n = 9.39 gram Co(NO₃)₂ / 182.93 gram/mol = 0.051 mol Co(NO₃)₂

Then, we divide the number of moles by the total solution volume to get concentration.

C = 0.051 mol / 0.3 L = 0.17 M

Answer: the concentration of cobalt(II) nitrate in the resulting solution is a 0.17 M.