1. Separation of a Mixture
NH4Cl, NaCl, and SiO2

2. NaCl and NH4Cl, Ionic Solids
Ionic bonds are much weaker than covalent bonds
Ionic Solids are Generally Soluble in water

3. Solvated Ions
The ions are happier in water than they are in NaCl(s)

4. NaCl – Rock Salt Melting point 801 °C Boiling point 1413 °C
2NaCl(l)  Na2(g) + Cl2(g)

5. NH4Cl – Ammonium Chloride
Melting point 338 °C (decomposes) (sublimation)
NH4Cl(s)  NH3(g) + HCl(g)

6. Silica Periodic Covalent Solid (glass) Insoluble
Melting point  °C
Boiling point  °C

7. Separating NH4Cl from Salt and Sand
A bunsen burner reaches around 1100oC in the hottest part of the flame
Ammonium chloride sublimes at 338oC
NaCl(s) melts at 801oC
SiO2 just gets hot!
So remove NH4Cl by heating

8. Separating Salt from Sand
Salt being an ionic solid is soluble in water, sand is not
We can remove the salt by dissolving the salt in water and decanting off the salt water (extraction)
Grams of NaCl w Sand + 10 mL H2O
Pour out 9/10 of the salt water grams NaCl removed in extraction
Grams NaCl remain with sand
1.0
0.9
0.1g
0.1
0.09
0.01g
0.01
0.009
0.001g
0.001
0.0009
0.0001g

9. Procedure
Take an unknown and record the id number of the unknown in your notebook
Weigh the evaporating dish and record the mass to 4 decimal places m1
Transfer ALL of the sample into the dish and reweigh m2
In a fume cupboard heat the dish and its contents using a Meker Burner
When the sample stops exuding white smoke, stir it with a glass stirring rod – more NH4Cl will probably be emitted. When no more smoke is seen and none deposits on the stirring rod, turn off the burner and let the dish cool
Reweigh the dish m3
Calculate the mass % of NH4Cl
Check with me before performing extraction
Add 10 mL of deionized water to the dish, stir with clean glass stirring rod
Being careful to not lose sand, pour out the water into a beaker, allowing water to flow down a glass rod, keeping the rod pushed up against the lip of the dish to prevent sand escaping
Repeat this last step 4 times in all. Dry sand with heat lamp, cool and re-weigh m4
Calculate the mass % NaCl