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Lab 7Chemicals in everyday life
Concepts– Positive test
• A test that deteemines a type of reaction based on a positive result.
– Can not detrmine based on a negative result
Part A
1. NH3 + H2O NH4
+ OH-
• Positive tests for NH3
• Warning! Ammonia is caustic
• Ammonia salts synthesises to ammonium in water
Part A
1. Read procedures for part A on page 68 and fill out 1 –6 pg 73
• Positive tests for NH3
• Warning! Ammonia is caustic
• Ammonium salts decompose to ammonia when there is a strong base
1. NH3 + H2O NH4
+ OH-
Part A
• Determine if fertilizers and smelling salts have ammonium in it by doing positive tests for ammonia
Part B• Warning H2SO4 and HCl causes severe
burns
Part B
1. CO3-2 + H+ CO2 + H2O
• Positive tests for baking soda (NaHCO3) austic
• Carbonates react with acids to produce carbon dioxide
Part B
• Add a small amount of baking soda to a dry test tube• Using a beral pipette add 1 or 2 drops of 18 M sulfuric acid• Note the color and odor of the escaping gas• Record observation and answer questions 7• Repeat procedure but use vinegar or acetic acid• Record observation and answer questions 8
– Warning fan the gas do not smell it!!
– Warning H2SO4 causes severe burns
• Do a positive tests for CO2 in baking soda
Part B
1. CO2 + BaOH BaCO3 (s) + H2O
• Determine if chalk contains carbon dioxide by doing Positive tests for carbon dioxide
• carbon dioxide and barium Hydroxide produces a white precipitate
Part B
• Add a small amount of chalk to a dry test tube
• Using a beral pipette add 1 or 2 drops of 2 M HCL
• Note the color and odor of the escaping gas
• Omit Barium Hydroxide
• Record observation and answer question 9– Warning fan the gas do not smell it!!
– Warning HCL causes severe burns
• Determine if chalk contains carbon dioxide by doing Positive tests for carbon dioxide
Part C
1. 2Cl- + H2SO4 2HCl(g) + SO4
-2
2. Cl- + AgNO3
NO3 + AgCl (s)
1. All Cl- salts react with sulfuric acid (H2SO4) to produce HCl (g)
2.All Cl- salts react with silver nitrate (AgNO3) to produce a white precipitate AgCl (s)
Part C
• Add a small amount of salt to a dry test tube
• Using a beral pipette add 1 or 2 drops of sulfuric acid
• Note the color and odor of the escaping gas
• Record observation and answer questions 10 and 11– Warning fan the gas do not smell it!!
– Warning H2SO4 causes severe burns
• Do a positive tests on table salt to test for Chloride ions
Part C
• Add a small amount of salt to a dry test tube
• Add 15 drops of distilled water
• Using a beral pipette add 1 drop of Nitric acid
• Using a beral pipette add 3 drops of silver nitrate
• Record observation and answer questions 12 – 13
– Warning HNO3 causes severe burns
• Do a positive tests on table salt to test for Chloride ions
Part C
• In a test tube add 2ml of tap water
• Using a beral pipette add 1 drop of Nitric acid
• Using a beral pipette add 3 drops of silver nitrate
• Record observation and answer questions 14
– Warning HNO3 causes severe burns
• Do a positive tests on Cl- ions in tap
Do not do procedures 15 or question 15
Part D
1. SO4 -2 + BaCl2 BaSO4(S) + 2 Cl-
SO4 -2
ions reacts with Barium chloride (BaCl2) to produce Barium sulfate BaSO4 (S)
•Read procedures for part D on pg 70 and fill out 16-17on pg 73
Part D• Positive tests for sulfates in Epson salt
• In a test tube add a small quantity of epson salt• Using a beral pipette add 1 or two drops of
Sulfuric acid• Record observation and answer question 16• Warning Sulfuric causes severe burns
Part D• Positive tests for sulfates in Epson salt
• In a test tube add a small quantity of epson salt• Add 1 ml of distilled water• Using a beral pipette add 1 or 2 drops of Nitric
acid• Using a beral pipette add 1 or 2 drops of
barium Chloride
• Record observation and answer question 17• Warning Sulfuric acid causes severe
burns
Part E (bleach)
NaOCl4- ion (bleach) acts like a Cl2
gas
Chlorine gas and Chlorine ion act very differently from each other
Chlorine gas can convert iodide salts to iodine giving water and reddish hue
Part E (bleach)• Positive tests for Iodide Salts
NaOCl4 ion (bleach) reacts with iodine salts to form iodine
(Cl2)(aq) + 2I- (I2)(aq) + 2 Cl-
Part E (Bleach)• Positive tests for chlorine in bleach
• In a test tube add a small quantity of Iodine salt• Add 1 ml of distilled water• Using a beral pipette add 5 drops of bleach• Add a few drops of mineral oil
• Record observation and answer question 18• Warning Bleach is corrosive
Part E (iodide salts)• Positive tests for Iodide Salts
iodide salts react with silver to form silver iodide, a pale yellow precipitate
AgNO3 aq) + I- (AgI)(s) + NO3-
Part E (iodide salts)• Positive tests iodide salts
• In a test tube add a small quantity of sodium iodide• Add 1 ml of distilled water• Using a beral pipette add 1 drops of Nitric acid• Using a beral pipette add 3 drops of silver nitrate
• Record observation and answer question 19• Nitric acid is corrosive
Part E (iodide salts)• Must be done in hood
• In a test tube add a small quantity of sodium iodide• In the hood using a beral pipette add 1 drops of Slfuric
acid
• Record observation and answer question 20• Sulfuric acid is corrosive
Part F (Unknowns)• Determine the type of ion your is unknown is
based on the results of a positive test with H2SO4 based on table 7.1 on page 71
• You solid unknown will contain one of the following ions– CO3 -2
, Cl - ,SO4 -2 , I -
Part F (? ions)
• In a test tube add a small quantity of your unknown compound
• Using a beral pipette add 1 drops of Sulfuric acid
• Record observation and based on table 7.1 answer question 21• Warning Sulfuric acid is corrosive
Due next week
• Pgs 73 – 74 omit page 75
• Pre Quiz on lab 8