What mass of Ca(NO3)2 must be dissolved in 726.0 g of water to prepare a 0.200 m solution? Use molar masses with at least as many significant figures as the data given.

The answer to your question is 22.4 g of Ca(NO₃)₂

Explanation:

Data

mass of Ca(NO₃)₂ = ?

mass of water = 726 g

concentration = 0.2 m

Process

In Chemistry, there are two main units of concentration Molarity (M) and Molality (m). In this problem concentration is "m" then I will calculate molality.

1) Formula

   molality = moles / mass of solvent

2.- Solve for moles

   moles = molality x mass of solvent

-Substitution

   moles = (0.2) x (0.726)

-Simplification

   moles = 0.1452

3.- Convert moles to grams

Molar mass of Ca(NO₃)₂ = 40 + (14 x 2) + (6 x 16)

                                       = 40 + 18 + 96

                                       = 154 g

              154 g of Ca(NO₃)₂ 1 mol

                 x                           0.1452 moles

                                    x = (0.1452 x 154) / 1

                                    x = 22.4 g of Ca(NO₃)₂

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