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class 11th cbse Some Basic concepts of chemistry

Dr Brian Cox takes us on a journey through the history of particle physics. In this episode we learn that the Greeks knew about atoms and how Mendeleyev's periodic table was among the first clues that the atom had a deeper structure.































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IS MATTER AROUND US PURE part 4

Exercises (pg 28-30)
1. What separation techniques will you apply for the separation of the following:
(a) Sodium chloride from its solution in water: Evaporation
(b) Ammonium chloride from a mixture containing sodium cholride and ammonium chloride: Sublimation
(c) Small pieces of metal in the engine oil of a car: Filtration
(d) Different pigments from an extract of flower petals: Chromatography
(e) Butter from curd: Centrifugation
(f) Oil from water: Separating Funnel
(g) Tea leaves from tea: Filtration
(h) Iron pins from sand: Magnet
(i) Wheat grains from husk: Winnowing
(j) Fine mud particles suspended in water: Filtration

2. Write the steps you would use for making tea, use the words – solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
(i) Take about 20ml of tap water (solvent) in a beacker.
(ii) Boil the water in a pan.
(iii) Put some tea leaves in a tea pot.
(iv) Pour some boiling water into the pot. It will form a solution.
(v) Put sugar (solute) into a cup.
(vi) Stir the solution in the tea pot.
(vii) Using a strainer, pour the solution into the cup.
(viii) Add two tea-spoons of milk.
(ix) Remove the strainer and stir with a spoon.
(x) The tea is ready and the leaves (residue) will be left on the strainer while tea (filtrate) will pass through the solution.

IS MATTER AROUND US PURE part 3

3. To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
Mass of solute = 36g
Mass of solvent = 100g
Mass of solution = Mass of solute + Mass of solvent
= 36g + 100g
= 136g
Concentration = Mass of solute/Mass of solution * 100%
= 36/136 * 100%
= 26.5%
Questions (pg 24)
1. How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25OC), which are miscible with each other.
(i) Take the mixture in a distillation flask and fit it with a thermometer.
(ii) Place a condenser outlet below and connect it to the distillation flask by using a water condenser.
(iii) Heat the mixture slowly by keeping a close watch at the thermometer.
(iv) The petrol vaporises, condenses in the water condenser and can be collected frm the condenser outlet.
(v) Kerosene is left behind in the distillation flask.

2. Name the technique to separate:
(i) butter from curd: centrifugation
(ii) salt from sea-water: evaporation
(iii) camphor from salt: sublimation

3. What type of mixtures are separated by the technique of crystallisation?
The mixtures whose components have different solubilities in water are separated by crystallisation.