Question

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.

Answer 1

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

Step-by-step 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