Question

Group 3 Bag C: KBr, m-nitrobenzoic acid, Benzophenone

Project 6: Properties of Matter and Separations Week 1: Prelab Organizational Questions 1. What is your group's unknown number and which compounds are in your group's unknown? 2. Draw the structures of your group's compounds. Be sure to include valence electrons. 3. Look up and record the solubility in water for each of your three compounds. 4. Define pka and list the pka of each of your solids. 5. How does pH of a solution affect solubility? 6. How does polarity affect solubility?

Answer 1

1) Group -3

It consists of KBr, m-nitrobenzoic acid and Benzophenone.

2)

K-Bri 65 CH m-nitrobenzoic acid Benzophenone

3) KBr is water soluble.

m-nitrobenzoic acid is slightly soluble in water.

Benzophenone is insoluble in water.

4) pKa indicates the strength of the acid. pKa is the negative log of the acid dissociation constant,Ka.

The lower the pKa value, the stronger the acid.

pKa of m-nitrobenzoic acid = 3.47

5) pH of a solution affects solubility. The solubility of many compounds depends strongly on the pH of the solution. For example, In many sparingly soluble salts the anion is the conjugate base of a weak acid that may become protonated in solution. The solubility of oxides and sulfides also depends on the pH. At low pH, the protonation of anion increases the solubility. In solutions containing mixtures of dissolved metal ions, pH can be used to control the anion concentration which required to selectively precipitate the desired cation.

6) Polar substances dissolves in polar solvent. As the polarity of the substance increases, it increases its solubility in polar solvents. Whereas non polar substances is more soluble in non polar solvent.