The Sense Organs and Chemistry_ Observations of Practical Chemistry and Lab Activities

One of the many things which makes Chemistry fun is Practicals. Wearing lab coats , pouring liquids together in delicate glass ware ,  experiencing an explosion in the back bench because of some careless friend. (Let's hope the last one doesn't happen), but this year most highschoolers had to miss these fun times in the lab due to online schooling. Simulations and Videos are useful but not as engaging as pouring acids and bases with your own hands, and along with missing memorable times with the bunsen burners, we also missed many important concepts related to practicals which might be asked in Boards.

In this blog, We will try to bridge few of these gaps experienced by highschoolers because of the missed lab practicals, Helping us answer any activities or practicals related MCQ's in the first term easily.

Colours of few common metals and salt solutions :-

CuS -- Black in colour 

ZnCl -- White in colour 

To check the release of gases during a reaction

1) Hydrogen -- Bring a burning splinter near it --- Extinguises with a POP sound.

                     -- Colourless and Odourless 

   Examples :- Zn + HCl --> ZnCl + H2 ↑  ( We also observe bubble formation) 

2) Oxygen -- Bring a glowing Splinter near it -- Burns even brighter.

                   -- Colourless and Odourless

  Example -- Photosynthesis! 

3) Carbon - di -  Oxide  -- Pass it through lime water (Ca(OH)2), created an insoluble (white)                                                             precipitate of CaCO3 and water.

                                         (* If excess of CO2 is passed -- forms Ca (HCO3)2 which is soluble in water.)

                                     -- Another way to test is to bring a burning splinter near the mouth of the test                                                 tube, it will extinguish

                                    -- Colourless and Odourless (Usually characterised as Brisk effervescence) 

  Example -- NaHCO3 + HCl --> NaCl + CO2 + H20

4) Sulphur - di - Oxide -- SO2 can reduce an acidified solution of Potassium Di Chromate 

                                         so basically 

                                    --Colourless and has odour of burnt Sulphur (Sulphur trioxide +Sulphur Di                                                  Oxide together)

                         II Method -

                          Pass SO2 through KMnO4 , First which is pink decolourises and forms a colourless                                 solution 

Example -- When FeSO4 is heated it releases Ferric Oxide + SO2 +SO3 

5) Nitrogen Di Oxide -- We can see 'Brown Fumes'

Example --Heating of Lead Nitrate 

6) Hydrogen Sulphide -- Smell of 'Rotten Eggs'

7) Br2 - Gives out Brown fumes

8) Cl2 - Gives out Greenish - Yellow Gas

9) Ammonia - Pungent Smell 

                        When it reacts with HCl -- Gives out NH4Cl ( Dense white fumes) 

Flame Test 

Various metals when heated in spirit lamp or bunsen burner produce flames of different colours:-

1) Pottasium -- Purple

2) Barium -- Green (Crimson Green or Apple Green)

3) Iron -- Reddish Glow

4) Strontium -- Crimson Red

5) Aluminium -- (Silvery)White

6) Copper -- Blue - Green

7) Lead -- Blue

8) Magnesium -- White

9) Sodium -- Yellow

Colour of Precipitates

If formed with the ions of

1) Cu 2+ -- Blue

2) Fe 2+ -- Green

3) Fe 3+ -- Reddish - Brown

4) Cr 3+ -- Orange

5) Mn 2+ -- Buff Pink

The Environment and Metal

and one extra point:- CaO + H2O -- gives 'hissing' sound 

Hope this blog helps you ace your Chemistry exam !