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Chemistry Notes

Anions: Test and characteristics of Anions

Test for Anions,

Identification of gases e.g CO2, SO2 and O2.

Characteristics test for anions e.g SO42-,SO32-,CO32-,NO-3, Cl–, etc.

The anions are negatively change ions examples of anions are SO42-,SO32-,CO32-,S2- etc.

Identifications of gases:

H2It gives a ‘pop’ sound when the gas is contact with a lighted splint.
O2It rekindles a glowing splint.
CO2It is colourless and odourless. It turns lime water milky.  
Cl2A green wish yellow gas, it turns moist iodide paper black.  
SO2Colourless gas with irritating smell. It turns damp blue litmus paper to red. That is acidic gas.

EVALUATION

  1. State two (2)  examples of anions with their gases.
  2. Identify Cl2 and NH3 gases.
test for SO4
test for SO4

GENERAL EVALUATION

  1. Give the common reagents for confirmatory test of anions
  2. State how you would confirm/test for NO3-
  3. Name three gases that are colourless and acidic to litmus.
  4. Sodium chloride and silver trioxonitrate(V) crystals are separately soluble in water to give colourless solutions. Explain what happens when their solutions are mixed together.

READING ASSIGNMENT

School Chemstry by O.Y Ababio pages 165 – 183

Practical Chemistry by R. I Makanjuola pages 27-33.

Practical Chemistry for Schools and Colleges by Godwin O. Ojokuku pages 30 – 98.

WEEKEND ASSIGNMENT
  1. Brown ring test is used to confirm (a) S2- (b)NO3- (c) SO42- (d) SO32-
  2. The presence of SO32- change the colour of acidified K2Cr2)7 from (a) green to red    (b) purple to colourless  (c) orange to green  (d) green to orange
  3. A greenish yellow gas that change moist iodide paper black is (a) Cl2   (b) SO2 (c) H2  (d) O2
  4. Sometimes in the presence of  conc HsSO4, copper turning and heat NO3- gives (a) brown ring reaction  (b) pure brown fume   (c ) reddish brown   (d) effervescence        
  5. The gas that turns lime water milky is (a) H2 (b) SO2 (c) NH3 (d) CO2.

THEORY

  1. State the colour of these solutions a. KMnO4 b. K2Cr2O3 c. HOBr d. CuSO4.5H2O e. Ca(OH)2
  2. Carry out the following exercises on sample K. add about 10cm3 of distilled water to K in a test tube. Divide the solution into four.
  3. To the 1st portion add NaOH  drop wise and in excess.
  4. To the 2nd portion add NH3 solution drop wise and then in excess.
  5. To the 3rd portion, add it drops of BaCl2 follow by the addition of dil HCl
  6. To the 4th portion, add dil HCl follow by the addition of BaCl2.

Record your observation and inferences then name the salt K.

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