Core Practical 7: Identify unknown organic liquids and inorganic solids

Question 1

unknown organic liquid must be treated as

Answer 1

harmful and flammable

Question 2

unknown inorganic solids must be treated as

Answer 2

harmful

Question 3

acidified potassium dichromate(VI) is

Answer 3

carcinogenic, corrosive and oxidising

Question 4

potassium manganate(VII) is

Answer 4

an oxidising agent

Question 5

ethanol is

Answer 5

flammable

Question 6

silver nitrate is

Answer 6

corrosive

Question 7

chlorine water is

Answer 7

toxic

Question 8

dilute ammonia

Answer 8

gives of an irritant gas

Question 9

0.1 mold dm-3 Barium chloride is

Answer 9

harmful

Question 10

the method for testing for the organic liquids is:

Answer 10

• place 10 drops of each liquid in separate test tubes labelled A,B, and C, and repeat to obtain four test tubes of each substance
• to the first lot of tubes, add 1cm3 of bromine water
• to the second, add K2Cr2O7 and H2SO4 and warm teh mixture to 60 degrees C for 5 minutes
• to the third lot, add 1cm3 of Fehling’s solution (blue solution containing the Cu2+ complex ion) and warm in warm water bath
• Add 1 cm3 of ethanol and 1 cm3 of dilute sodium hydroxide solution to each test tube and warm the mixture in a water bath for five minutes. Acidify each mixture with dilute nitric acid and then add 5 drops of silver nitrate solution.

Question 11

the method for testing the inorganic solids is:

Answer 11

• perform flame tests on solids X,Y and Z by using a silica or platinum wire loop dipped in concentrated HCl acid to dissolve a bit of the solid onto the loop, then hold in the roaring flame of a Bunsen burner
• Dissolve a spatula full of each solid in three separate test tubes containing 10 cm3 distilled water. Split each solution into three portions
• to the first lot, add 5cm3 dilute nitric acid, then 10 drops of silver nitrate solution, then add dilute and then concentrated ammonia solution (observe whether a precipitate dissolves)
• to the second, add 5cm3 dilute nitric acid, then 10 drops of barium chloride solution
• to the third, add 2cm3 of chlorine water (this tests for bromine, as an orange solution will form as Cl2 displaces Br- ions to form Br2 and Cl- ions)