Separation of a Mixture NH4Cl, NaCl, and SiO2

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

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

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

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

Silica Periodic Covalent Solid (glass) Insoluble Melting point 1600-1725 °C Boiling point 2230 °C

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

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

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