CPrac J - QA

State solubility table

NO3-	All soluble
CI-, Br-, I-	All soluble except Ag+ and Pb2+
SO4^2-	All soluble except Ca2+, Ba2+ and Pb2+
CO3^2-	All insoluble except Na+, K+ and NH4+
OH-	All insoluble except Na+ and K+ (Ca(OH)2 slightly soluble)
Na+, K+, NH4+	All soluble

Describe gases + their reaction with water (NH3, CO2, CI2, H2, O2, SO2, NO2)

NH3	Basic, colourless, pungent NH3 + H2O -> NH4+ + OH-
CO2	Acidic, colourless CO2 + H2O -> H2СО3 Test: Pass the gas evolved through a delivery tube which has one end immersed in limewater
CI2	Acidic, pale yellow-green, swimming pool smell CI2 + H2O → HCI + HCIO
H2	Neutral, colourless
O2
SO2	Acidic, colourless, smell of burning sulfur / paper SO2 + H2O -> H2SO3
NO2	Acidic, pale brown, choking 3NO2 + H2O → 2HNO3 + NO

State deduction of the gases

State deductions from these observations

• If warming is required after adding NaOH(aq)…

• If warming is required after adding NaOH(aq) and Al foil…

• If warming is required after adding NaOH(aq), test for ammonia gas -> A positive test indicates that NH4+ is present.

• If warming is required after adding NaOH(aq) and Al foil, test for ammonia gas -> A positive test indicates that NO2− or NO3− is present

If NaOH(aq) is added to a solution, look out for the formation of any ppt., note its colour and solubility in excess NaOH(aq) 

For Fe3+, AI3+, Cr3+

Acidic enough to react with Na2CO3 OR NaHCO3 to produce CO2 and hydroxide ppt 

Explain how AI3+ forms white ppl soluble in excess with NaOH(aq)

Eg. AI3+

• On adding NaOH(aq), Al3+(aq) gives a white precipitate of Al(OH)3 which is soluble in excess NaOH(aq) to give colourless Al(OH)4- ions

• When HNO3(aq) is added, the acid removes the excess NaOH(aq) present, POE shifts left -> white Al(OH)3 ppt reforms 

• Al(OH)3(s) + OH-(aq) = Al(OH)4-(aq)

When Ba(NO3)2 OR BaCI2 added, MUST include…

• Ppt 

• Solubility of ppt in acid 

• Any gas formed

State colour of element, colour in aq and organic solution in hexane for CI2, Br2, I2

Add dilute acid can test for… (give observation and deduction)

Add dilute acid can test for… (give observation and deduction) #2

Add AgNO3 can test for… (give observation and deduction)

Add Ba(NO3)2 or BaCI2 can test for… (give observation and deduction)

Addition of KBr to unknown solution can test for… (give observation and deduction)