Question

Determine the concentrations of BaBr2, Ba2 , and Br– in a solution prepared by dissolving 2.14 × 10–4 g BaBr2 in 1.75 L of water. Express all three concentrations in molarity. Additionally, express the concentrations of the ionic species in parts per million (ppm).

[BaBr2]=

[Ba^2+]=

[Br^-]

Answer 1

1. Assuming all the barium bromide dissolved (which it should), the concentration of BaBr2 in solution should be zero:

2. it should all dissociate into Ba+2 and 2Br- ions

3. . Turn those grams of BaBr2 into moles of BaBr2, then divide by the volume to get the concentration.

4. Recognize that every formula unit of BaBr2 has one ion of Ba+2, and 2 ions of Br-1.

5. That means that when this substance dissociates, you'll get one concentration of Ba+2 ions, and a concentration of Br- ions TWICE as large.

6. Whatever the concentration of Ba+2 ions is that you calculate, double it for the conentration of the Br^-1 ion