Grade 10 Chemistry Week 3 – Precipitate Reactions                        Name _________________

1. What is a precipitate?
   
   
   
   
   
2. How would you distinguish a precipitate from a solution?
   
   
   
   
   
3. Define the terms:
   
   Crystalline precipitate: _______________________________________________________
   
   Gelatinous precipitate: _______________________________________________________
   
   Amorphous precipitate: ______________________________________________________
   
   
4. You mix silver nitrate (AgNO3) solution with potassium chloride (KCl) solution and notice a precipitate of silver chloride forms. Represent with the aid of diagrams what is happening:
   
   Before:                                        After:
   
   
   
   
   
   
   
   
   
   
5. How would you separate out the silver chloride precipitate from the potassium nitrate solution that you obtained by reacting the chemicals in Question 5?
   

6. Reacting copper sulfate (CuSO4) solution with sodium hydroxide (NaOH) solution will produce a precipitate of copper hydroxide. List the series of steps you would go through to prepare dry copper hydroxide and dry sodium sulfate (which are the products of the reaction).
   

Going further

7. The solubility rules for various cations and anions are as follows:

1. Alkali metal (Group 1) compounds are soluble. That means Li+, Na+, K+ compounds are soluble.

2. Ammonium (NH4+) compounds are soluble.

3. Nitrates (NO3-), chlorates (ClO3-), and perchlorates (ClO4-) are soluble.

4. Most hydroxides (OH-) are insoluble.

The exceptions are the alkali metal hydroxides and Ba(OH)2.
Ca(OH)2 is slightly soluble.

5. Most chlorides (Cl-), bromides (Br-) or iodides (I-) are soluble.

The exceptions are those containing Ag+, Hg+, and Pb2+.

6. Carbonates (CO32-), phosphates (PO43-) and sulfides (S2-) are insoluble.

The exceptions are the alkali metals and the ammonium ion.

7. Most sulfates (SO42-) are soluble.

CaSO4 and Ag2SO4 are slightly soluble.
BaSO4, HgSO4 and PbSO4 are insoluble.

Use the solubility rules to help predict whether a reaction will occur and what the products will be for:

1. Barium chloride solution mixing with sodium sulfate solution.
   
   Does a reaction occur? (yes/no).   If yes, what are the products?
   
   
   If there is a reaction, have a go at writing a balanced equation for the reaction:
   
   
   
   
2. Silver nitrate solution mixing with potassium iodide solution.
   
   Does a reaction occur? (yes/no).   If yes, what are the products?
   
   
   If there is a reaction, have a go at writing a balanced equation for the reaction:
   
   
   
   
3. Potassium nitrate solution mixing with sodium bromide solution.
   
   Does a reaction occur? (yes/no).   If yes, what are the products?
   
   
   If there is a reaction, have a go at writing a balanced equation for the reaction:
   
   
   
   
4. Mercury(II) chloride mixing with mercury(I) nitrate.
   
   Does a reaction occur? (yes/no).   If yes, what are the products?
   
   
   If there is a reaction, have a go at writing a balanced equation for the reaction:
   
   
   
   
   

Going much further

8. Are there any common compounds which are partially soluble (dissolve a bit) in water? Use the “slightly soluble” list from the solubility table on page 2 to help you.
   
   
   
   
   
   
   
   In fact nearly all precipitates are very, very, very slightly soluble. The solubility product Ksp is defined as the product of the concentration of ions raised to the power that they appear in the chemical formula. For instance the solubility product for calcium fluoride CaF2 is
   
                                   Ksp = [Ca2+][F-]2
   
   Here the square brackets refer to the concentration which is usually measured in M (which stands for moles per litre).
   
   (a) If Ksp = 4.0 x 10-11 for calcium fluoride, what is the maximum concentration of calcium fluoride that will dissolve in water?
   
   
   
   
   
   
   
   
   
   (b) If Ksp = 5.0 x 10-13 for silver bromide, what is the maximum concentration of silver bromide that will dissolve in water?
   
   
   
   
   
   
   
   
   (c) If Ksp = 6.3 x 10-50 for silver sulphide, what is the maximum concentration of silver sulphide that will dissolve in water?