Chapter 11 Practical Work Frank Class 9 Frank Chemistry

Frank Solutions for Chapter 11 Practical Work Class 9 Chemistry ICSE

1. What is sublimation? Give two examples.

Answer

On heating certain solids they don’t meh and directly get converted to their gaseous form, this process of direct conversion of solids to their gaseous form is called as sublimation. For

ex: camphor and ammonium chloride undergo sublimation.

2. What is decrepitation? Which salt decrepitate on heating?

Answer

Decrepitation is a process of breaking up of solid particles on heating, which makes a crackling sound. Lead nitrate decrepitate on heating.

Pb(NO₃)₂ → 2PbO + 4NO₂  + O₂

Pb(NO₃)₂: Lead nitrate

3. Give the colour of the following compounds.

(a) Zn(NO)₃

(b) Cu(NO₃)₂

(c) CuSO₄.5H₂O

(d) CuSO₄

(e) K₂Cr₂O₇

(f) PbS

Answer

(a) Zn(NO)₃ : white

(b) Cu(NO₃)₂ : blue

(c) CuSO₄.5H₂O : blue

(d) CuSO₄ : pale green

(e) K₂Cr₂O₇ : orange

(f) PbS : black

4. How will you distinguish between:

(a) NH₃ and Cl₂

(b) CO₂ and SO₂

(c) H₂S and SO₂

(d) H₂ and O₂

Answer

(a) Difference between NH₃ and Cl₂

NH3	Cl2
The gas is colourless and pungent odour it turns blue litmus red and it produces white dense fumes when a rod dipped in conc. HCl is brought near the gas.	The gas is greenish yellow and has a pungent smell.

(b) Difference between CO₂ and SO₂

CO2	SO2
It is odourless and colourless, it turns lime water milky and on passing excess of gas through it the milkiness disappears.	It is colourless and smells like burning Sulphur it turns orange potassium dichromate paper green.

(c) Difference between H₂S and SO₂

H2S	SO2
It is colourless and smells like rotten eggs, it turn lead acetate paper black.	Colourless and it smells like burning Sulphur it turns orange potassium dichromate paper green.

(d) Difference between H₂ and O₂

H2	O2
It will extinguish a lighted splinter and the gas burns with a ‘pop’ sound.	It will relight a glowing splinter and absorbed by an alkaline solution of pyrogallol to turn it dark brown.

5. Differentiate between

(a) Hard water and soft water

(b) Temporary hardness and permanent hardness

(c) Soaps and detergents

Answer

(a) Difference between hard water and soft water

Hard water	Soft water
By stirring hard water thoroughly with ordinary soap, we get scum.	By stirring soft water thoroughly with ordinary soap, we get foam or lather formation.

(b) Difference between temporary hardness and permanent hardness

Temporary hardness	Permanent hardness
Addition of soap to the boiled water with temporary hardness makes the water soft and then it gives lather easily.	Addition of soap to the boiled water with permanent hardness does not make the water soft and its hardness still persist.

(c) Difference between soaps and detergents

Soaps	Detergents
It does not form lather with hard water.	It can form lather with hard water.

6. (a) What chemical test you can perform in laboratory to verify that given piece of metal is zinc not copper?

(b) Give a chemical test to distinguish between Na7S and Na2Co3.

(c) How will you perform a flame test for sodium?

Answer

(a) Chemical test to verify that given piece of metal is zinc not copper:

Take a small quantity of the given piece of metal in a clean and dry test tube. To that 10 ml of dilute sulphuric acid is added ,if effervescence are observed and a colourless and odourless gas which bums with a pop sound when a burning splinter is brought near its mouth and some water droplets are formed then the metal is zinc not copper.

(b) Chemical test to distinguish between Na₂S and Na₂Co₃.

(c) Flame test:

1. Clean the free end of the platinum wire fused in a glass rod, by repeatedly heating it in a flame and again dipping it in conc. hydrochloric acid taken in a watch glass.
2. Place it on non luminous part of the flame if it imparts colour then dip it in HCl again, until it fails to impart colour to the flame.
3. Touch the tip of clean platinum wire with conc. HCl and little substance, and place it in non luminious part of Bunsen burner flame.
4. The colour of the flame is observed by the naked eye, with sodium it shows a golden yellow flame.

7. Describe the effect of heat on the following, and also write equations for each.

(a) Copper carbonate

(b) Washing soda

(c) Lead nitrate

(d) Ammonium chloride

Answer

Effect of heat on:

(a) Copper carbonate:

(b) Washing soda:

(c) Lead nitrate:

(d) Ammonium chloride:

8. Fill in the blanks:

(a) The gas with ____ smell is hydrogen sulphide.

(b) Smell of sulphur dioxide is like that of ___.

(c) A gas with irritating odour is__.

(d) _____ turns red litmus paper blue.

(e) The formula of lime water is ___.

(f) The ____ colour is imparted to flame by potassium.

(g) The calcium imparts _____ colour to the flame.

Answer

(a) Rotten egg

(b) Burning sulphur

(c) Nitrogen dioxide

(d) Alkali

(e) Ca(OH)₂

(f) Lilac

(g) Brick-red

9. What do you understand by paint and non point sources of water pollution?

Answer

• Point sources of water pollution: Sources of water pollution that discharge directly into the water source are called as point sources of water pollution.
  For example: factories
• Non point sources of water pollution: sources of water pollution that remain scattered and don't have specific locations for the discharge of pollutants into particular water bodies are called as non point sources of water pollution.
  For example: run off from fields.

10. Give atleast three parameters which should be determined to test quality of water and also give their standards available.

Answer

Parameters which should be determined to test quality of water are:

Parameters	Acceptable
Hardness	It should be between 200-600 mg
pH	It should be between 7.00-8.00
Specific conductance	For 25°, it is 300 ×10-6 mhos