Q1 |
Which separation techniques will you apply for the separation of the following?
(a) Sodium chloride from its solution in water.
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
(c) Small pieces of metal in the engine oil of a car.
(d) Different pigments from an extract of flower petals.
(e) Butter from curd.
(f) Oil from water.
(g) Tea leaves from tea.
(h) Iron pins from sand.
(i) Wheat grains from husk.
(j) Fine mud particles suspended in water. |
Ans: |
a. Evaporation
b. Sublimation
c. Filtrations
d. Chromatography
e. Centrifugation
f. Separating funnel
g. Filtration
h. Magnetic separation
i. Winnowing
j. Centrifugation |
|
Q2 |
Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue. |
Ans: |
Steps :
-
Take 100 ml of water in a pan on a solvent.
-
Boil it for few minutes
-
Add 1 teaspoon tea leaves, add 1 and half tea spoon sugar and 50 ml of milk in a pan. Here, sugar, tea leaves and milk behave like a solute.
-
Boil it for a few minutes until the sugar dissolves in water and tea leaves and milk also devolve in water. As sugar, tea leaves are soluble in water to form solutions.
-
The prepared solution is passed to the tea retainer.
-
The insoluble tea leaves remain in the tea retainer as residue.
-
The tea (solution) is collected in the cup as filtrate.
|
|
Q3 |
Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).
Substance Dissolved
Tem
per
atu
re
in K
283
293
313
333
353
Potassium nitrate
21
32
62
106
167
Sodium chloride
36
36
36
37
37
Potassium chloride
35
35
40
46
54
Ammonium chloride
24
37
41
55
66
(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?
(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?
(d) What is the effect of change of temperature on the solubility of a salt? |
Ans: |
(a). 62 gm Potassium nitrate dissolved in 100 gm of water
62 / 2 = 31 gm
Potassium nitrate dissolved in 50 gm of water.
(b). In the given table, we see Potassium chloride solubility at different temperature then solubility was increased as the temperature was increased. An temperature decrease the solubility of Potassium chloride was decreased and the remains potassium chloride at higher lower temperature precipitate out.
(c). Ammonium chloride
(d). Solubility was increased as the temperature was increased. |
|
Q4 |
Explain the following giving examples.
(a) saturated solution
(b) pure substance
(c) colloid
(d) suspension |
Ans: |
(a) A solution in which no more solute can be dissolved at a particular temperature. i.e. it contains the maximum amount of salute. Example: an aqueous sugŠ°r solution in which more sugar cannot be added.
(b) The substance which is formed by only one kind of particle and having a constant. Composition of chemicals and characteristics. Properties throughout the sample. Example :- sugar and salt contains only one kind of particle and have the name composition throughout.
(c) It is a heterogeneous mixture having salute size greater than Ihm and smaller than 100 mm. They can scatter beams of light passing through. Example :- in milk, rubber, clouds etc.
(d) These are heterogenous mixtures of solids dispersed in liquids. The solute particles are insoluble and remain suspended throughout the bulk of medium. the solute size is greater than 100 mm. Example - dust article in air, muddy water etc
|
|
Q5 |
Classify each of the following as a homogeneous or heterogeneous mixture.
soda water, wood, air, soil, vinegar, filtered tea. |
Ans: |
Homogenous mixture: Uniform composition of constituents.
Heterogenous mixture: Non-uniform composition of constituents.
Homogenous Heterogenous
- Soda water - wood (C,O,H,N)
- Vinegar - air (O2, N2, H2,Co2, etc)
- Filtered tea - soil |
|
Q6 |
How would you confirm that a colourless liquid given to you is pure water? |
Ans: |
Take a sample of colourless liquid, put it on the stove and if it starts boiling at exactly 100* c, then it confirms that it is a pure water. Any other colourless liquid such as vinegar will always have a different boiling point.
|
|
Q7 |
Which of the following materials fall in the category of a “pure substance”?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air. |
Ans: |
Which shows constant composition throughout i.e it is made of one type of atom, element or compound is known as pure substance.
(a) Ice
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury |
|
Q8 |
Identify the solutions among the following mixtures.
(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water. |
Ans: |
Solution: In which the solute is evenly distributed in the solute. e.g.:- salt water
(b) Sea water
(c) Air
(e) Soda water is the solution among the following mixtures.
Air in a gaseous solution and soda water is a liquid solution. |
|
Q9 |
Which of the following will show “Tyndall effect”?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution. |
Ans: |
Tyndall effect: It is the property of colloidal solutions. The particle of colloidal solution can scatter light.
(b) Milk and (d) Starch solution shows tyndall effect.
But (a) Salt solution and (c) Copper sulphate solution is a true solution. |
|
Q10 |
Classify the following into elements, compounds and mixtures.
(a) Sodium
(b) Soil
(c) Sugar solution
(d) Silver
(e) Calcium carbonate
(f) Tin
(g) Silicon
(h) Coal
(i) Air
(j) Soap
(k) Methane
(l) Carbon dioxide
(m) Blood |
Ans: |
Elements: Elements cannot break in similar particles because it is also a similar particle. e.g. fe, H etc. Sodium, Silver, Tin, Silicon
Compound: When two or more than two elements are chemically combined known as compound. eg.: H2O. Calcium carbonate, Methane, Carbon Dioxide.
Mixture: It is a physical combination of two or more substances because there is no chemical reactions occur between them. Soil, Sugar Solution, Coal, Air, Soap, Blood. |
|
Q11 |
Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron filings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle. |
Ans: |
(a). Growth of a plant is a chemical change because at the time of photosynthesis, plants convert sunlight into chemical energy and this is an irreversible process.
(b). Rusting of iron is a chemical change because there is formation of new substance i.e.- Fe2O3, xH2O (Rust).
(c). Mixing of iron filings and sand is a physical change process.
(d). Cooking of food in a chemical change because there is change in chemical composition by supplying heat in addition to some food additives, oil, butter etc.
(e). Digestion of food is à chemical change because the enzyme present in stomach are break large macromolecules into simple molecules.
(f). Freezing of water is a physical change. because there is change in physical state of water notinitis composition.
(g). Burning of a candle is a chemical change because there is emission of CO2 and water vapours during the burning of candles. |
|