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Qualitative Analysis (presence of anions (test for sulfate (acidify…
Qualitative Analysis
presence of anions
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test for nitrate
acidify solution (with HCl) before adding aluminium foil and warming the mixture. effervescence observed, gas given off turns moist red litmus paper blue
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test for carbonate
add HCl, test for CO2 gas. effervescence observed, gas given off forms white precipitate with limewater
presence of cations
add sodium hydroxide
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Pb2+: forms white precipitate which is soluble is excess NaOH, forming a colourless solution (to differentiate from Al3+ add NaCl or HCl to form PbCl which is a white ppt while AlCl3 is soluble)
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Al3+: forms white precipitate which is soluble is excess NaOH, forming a colourless solution
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Zn2+: forms white precipitate which is soluble in excess NaOH, forming a colourless solution
NH4+: no precipitate, gives off ammonia gas which turns red litmus paper blue on heating. no change is observed when NaOH added in excess
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add aqueous ammonia
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Zn2+: forms white precipitate which is soluble in excess NaOH, forming a colourless solution
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Cu2+: forms light blue precipitate which is soluble in excess NH4OH, forming a dark/deep blue solution
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identifying gases
pungent
Cl gas turns blue litmus paper red, then bleaches red litmus paper
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