Q1. Give the difference between true solution, colloidal solution and suspension.
Ans. The difference between true solution, colloidal solution and suspension
Q2. State the different types of colloids with examples.
Ans. Different colloids are formed due to different dispersed phase and dispersing medium.
Q3. (a) Define solution. (b) Give different types of solutions with one example each.
Ans. (a) solution: It is a homogeneous mixture of two or more substances. It consists of solute and solvent.
(b) Different types of solution:
(i) Based on solvent—Aqueous and non-aqueous Aqueous solution has water as solvent (sugar + water) Non-aqueous solution has some other solvent but not water. Example, (sulphur + carbon disulphide)
(ii) Depending on the amount of solute dissolved in solvent—Dilute solution and concentrated solution Dilute solution—Less amount of solute particles are present in a solvent.
Concentrated solution—Amount of solute present in its maximum capacity in a solvent.
(iii) Amount of solute present in its maximum capacity at a given temperature— Saturated and unsaturated solution. Saturated solution—It is a solution in which no more solute can further dissolve in a given solvent at a given temperature.
Unsaturated solution—It is a solution in which some more solute can dissolve in a solvent at a given temperature.
(iv) Depending on the size of solute particles
Q4. How can you separate the following mixtures?
(a) Sand + iron (b) Cream from milk (c) Salt + water (d) Ammonium chloride + NaCl (e) Copper sulphate + water (f) Rice and dal (uncooked) (g) Gases from air (h) Petrol and diesel from crude oil (i) Drugs from blood (j) Acetone from water
|(a) Sand + iron||− magnetic separation|
|(b) Cream from milk||− centrifugation|
|(c) Salt + water||− evaporation|
|(d) Ammonium chloride + NaCl||− sublimation|
|(e) Copper sulphate + water||− crystallisation|
|(f) Rice and dal (uncooked)||− hand picking|
|(g) Gases from air||− fractional distillation|
|(h) Petrol and diesel from crude oil||− fractional distillation|
|(i) Drugs from blood||− chromatography|
|(j) Acetone from water||− distillation|
The Rf value of the mixture used in chromatogram is: A = 0.4, B = 0.5, C = 0.7, D = 0.9
(a) Calculate the Rf value of the two chromatograms shown in the figure.
(b) Name one solvent used in chromatography.
(c) Why is the line used for spotting drawn with pencil?
(d) If the chromatograms are colorless how can you locate them on the paper?
Ans. (a) Use scale to find the solvent front and find the Rf value by using the above formula.
(b) Water and alcohol.
(c) The pencil will not interfere in the chromatography.
(d) By using the locating agent like ninhydrin the colorless spots can be detected.
Q6. A metal coin is dissolved in acid. Chromatography is used to test the solution formed. The diagram given shows the chromatogram obtained.
(a) Describe how the chromatogram would be set up in the laboratory.
(b) What can you say about the composition of the coin?
(c) Which of the spots (A, B or C ) is more soluble in the
solvent that was used in the chromatography?
Ans. (a) To set up the chromatogram use the solvent, take chromatography paper and draw the base line with pencil, place the spot of the chromatogram on this line and dip it in the solvent such that the base line of the paper stays above the solvent line.
(b) The coin consists of three different materials as the chromatogram shows three spots.
(c) The spot B is more soluble in the solvent as it travelled the maximum distance.
Q7. Compare the simple distillation and fractional distillation.
Ans. simple distillation: The distillation flask is used to separate two substances having the difference in their boiling point more than 23 degrees. fractional distillation: The fractionating column in the set up helps in the separation of the fractions which may have very low difference in their boiling point. The fractionating column is a long chamber which controls the separation of one fraction at a time starting from the one with the lowest boiling point.
1. Let us divide the class into groups A, B, C and D.
Some other examples of mixtures are:
(i) salt dissolved in water.
(ii) sugar dissolved in water.
Example: Mixture of sodium chloride and iron fillings, salt and sulphur; and oil and water are examples of heterogeneous mixtures.
Is the mixture stable or do the particles begin to settle after sometime?
Question: Why a separating funnel is used?
Answer: Separating funnel is used to separate two immiscible liquids, because the two layers are formed depending on their densities and the liquids can be separated.
Group I: Mix and crush iron filings and sulphur powder.
Q1. Anil’s sister accidentally added some water into the bottle containing olive oil and she was afraid of the scolding. Anil helped his sister and separated the water from olive oil using bottle as separating funnel.
(a) What is the principle of using and working of separating funnel?
(b) Suggest two separation techniques used to separate liquid mixtures.
(c) What value of Anil is seen in the above case?
Ans. (a) The principle of separating funnel is difference in the densities of two liquids.
(b) Liquid mixtures can be separated by distillation and fractional distillation. (c) Anil showed the value of helping, caring and responsible behaviour.
Q2. Preeti saw a labour entering into the sewage manhole immediately after removing the lid. She promptly stopped the labour from entering into the manhole and told him to wait for some time before he enters into it.
(a) What will happen if the labour immediately enters into the manhole (for cleaning) after removing the lid?
(b) Name main gases that are released from the manhole.
(c) What value of Preeti is seen in the above act?
Ans. (a) If the labour immediately enters the manhole on removing its lid he would die due to suffocation and inhalation of poisonous gases which are compressed and released by sewage.
(b) Gases released from the sewage manhole are methane, carbon dioxide and hydrogen sulphide.
(c) Preeti shows the value of moral responsible behaviour and aware citizen.
Q3. Prasanna wanted to buy a deodorant from the shop. While buying a bottle he felt that it was slightly heavier than usual deodorant bottle that he purchased everytime. He read the weight mentioned on the bottle and told the shopkeeper to weigh the same. He found the bottle was heavy and on opening the deodorant bottle he found it half-filled with water. He complained the matter to the consumer authority.
(a) Define density.
(b) Apart from water what is the other substance that some shopkeepers add into the deodorant.
(c) What value of Prasanna is reflected in this act?
Ans. (a) Density of any substance is defined to be the mass of the substance per unit volume.
(b) One can add some cheap gases or compressed air in the deodorant bottles.
(c) Prasanna showed the value of being having leadership quality, rightful, aware and responsible citizen.
Q4. Rita’s father always got his vehicle checked for pollution control. He got it tested for the aerosol if released by his car. He also uses unleaded petrol and makes use of public transport wherever possible. He sparingly use his car.
(a) What is aerosol?
(b) What happens when smoke released from vehicle mixes with fog?
(c) What are the values of Rita’s father is reflected here?
Ans. (a) When the solid or liquid is dispersed in a gas it is called aerosol e.g. smoke.
(b) When smoke mixes with fog it forms smog.
(c) Rita’s father is an aware citizen, environmentally concerned and dutiful.
Practical Based Questions (Solved)
Q1. A student was given a mixture containing copper oxide (insoluble) and copper sulfate (soluble) and asked to separate them. Firstly, she stirred the mixture into water, then filtered it. Next, she evaporated the filtrate.
(a) What substance was the residue in the filtration?
(b) Describe what the filtrate was.
(c) What difference in properties allows substances to be separated by filtration?
(d) What substance was collected by evaporation?
Ans. (a) copper oxide
(b) A solution of copper sulphate
(c) Particle size
(d) Solid copper sulphate
Q2. Sandy is learning to cook. He accidentally mixed the icing sugar with the corn flour and spilled some raw rice grains into it as well. (Icing sugar and cornflour are both fine powders. Icing sugar is soluble, cornflour is not.) To separate this mess, he firstly sieved it. What went through the sieve he stirred into water, and let it stand overnight? In the morning a sediment had formed. He carefully poured the clear liquid into a tray and put it into the warm oven to evaporate.
(a) What was caught by the sieve?
(b) What difference in properties allows substances to be separated by sieving?
(c) What was the sediment?
(d) What solid will be in the oven tray when dry?
(e) What other method might Sandy have used to collect the substance which was a sediment?
Ans. (a) Rice
(b) Particle size
(c) Corn flour
(d) Icing sugar (or just sugar)
Q3. Name the technique(s) which are suitable for separating the following mixtures:
Q4. The following diagram shows a set-up of a simple distillation.
Identify the distillate collected in the receiver. How would you determine that the distillate collected is a pure substance?
Ans. On boiling sea water the water boils and turns into gas and then condensed as the distillate. A pure substance boils at a fixed temperature and the same can be noted on the thermometer in the apparatus.
Q5. A mixture of pebbles, fine sand and salt was sieved. What passed through the sieve was mixed with water and allowed to stand? A sediment formed. The clear liquid was poured off and evaporated. The sediment was also dried. Use a flowchart to show the procedure and what was collected.
Q6. A mixture of salt, water and chalk dust (insoluble) was filtered. The residue was dried. The filtrate was divided into two parts. One part was evaporated, the other part was distilled. Construct a flowchart and show what was collected at each step.