InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A mixture of sulphur and carbon disulphide isA. heterogeneous and shows tyndall effectB. homogeneous and shows tyndall effectC. heterogeneous and does not show tyndall effectD. homogeneous and does not show tyndall effect |
| Answer» Correct Answer - ( c) | |
| 2. |
The substance which is in more quantity is known as?A. SolventB. SoluteC. SolutionD. All of the above |
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Answer» Correct Answer - A |
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| 3. |
Rusting of an article made up of iron is calledA. corrosion and it is physical as well as a chemical changeB. dissolution and it is a physical changeC. corrosion and it is a chemical changeD. dissolution and it is a chemical chanage |
| Answer» Correct Answer - ( c) | |
| 4. |
(a) What mass of potassium chloride would be needed to form a saturated solution in 50 g of water at 298 K ? Given that solubility the salt is 46/100 g at this temperature. (b) What will happen if this solution is cooled ? |
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Answer» (a) Mass of potassium chloride in 100 g of water in saturated solution = 46 g Mass of potassium chloride in 50 g of water in saturated solution = `((46 g))/((100 g)) xx (50g) = 23 g` (b) When the solution is cooled, the solubility of salt in water will decrease. This means that upon cooling, it will start separating from the solution in crystalline form. |
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| 5. |
(a) State one property in which a solution of sugar in water resembles a mixture of sugar and sand and one property in which it differs from it. (b) You are given two liquids, on a solution and the other a compound. How will you distinguish the solution from the compound ? |
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Answer» (a) Resemblance : Both of them taste sweet due to the presence of sugar. Difference : The constituent particles cannot be seen in the mixture of sugar and water but they can be easily seen in the mixture of sugar and sand. (b) Try to separate the constituents present in both by some suitable physical method. Separation is possible in case of a solution but not in a compound. |
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| 6. |
On heating, calcium carbonate gets converted into calcium oxide and carbon dioxide. (a) Is this a physicl or a chemical change ? (b) Can you prepare one acidic and one basic solution by using the products formed in the above process ? If so, write the chemical equation involved. |
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Answer» (a) It is chemical change. The chemical equation for the reaction is : calcium carbonate `overset("heat")rarr` Calcium oxide + Carbon dioxide (b) By adding water to calcium oxide taken in a test tube, a basic solution results. It contains calcium hydroxide Calcium oxide + Water `rarr` Calcium hydroxide By passing carbon dioxide through water taken in a tube, carbonic acid is formed. The solution is of acidic nature Carbon dioxide + Water `rarr` Carbonic acid Notes : All the three chemical equations are word equations. Symbol equations can also be written for these. For example, `CaCO_(3) overset("heat")rarr CaO + CO_(2)` `CaO + H_(2)O rarrCa(OH)_(2)` (basic solution) `CO_(2) + H_(2)O rarr H_(2)CO_(3)` (acidic solution) However, you will learn about these in the next class. |
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| 7. |
Rusting of an article made up of iron is calledA. corrosion and it is a physical as well as chemical changeB. dissolution and it is a physical changeC. corrosion and it is a chemical changeD. dissolution and it is a chemical change. |
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Answer» Correct Answer - C corrosion and it is a chemical change. |
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| 8. |
Explain why particles of a colloidal solution do not settle down when left undisturbed while in the case of a suspension, they do. |
| Answer» In a colloidal solution, the particle size is smaller as compared to particle size in a suspension. The effect of gravity on these particles is less than in a suspension. Therefore, the particles in a suspension settle under the influence of gravity while they remain dispersed in a colloidal solution. | |
| 9. |
What would you observe when : (a) A saturated solution of potassium nitrate prepared at `60^(@)C` is allowed to cool to room temperature ? (b) A mixture of iron filings and sulphur is heated strongly ? (c ) A colloidal solution of starch is passed through an ordinary filter paper ? |
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Answer» (a) Crystals of potassium nitrate which are needle shaped would slowly appear at the bottom of the container which may be a china dish or a beaker. (b) A greyish-black mass passes formed. (c ) The solution passes through the ordinary filter paper without leaving any residue. |
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| 10. |
Calculate the mass of potassium sulphate required to prepare its 10 percent (mass percent) solution in 100 g of water. |
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Answer» Mass percent = `("Mass of solute")/("Mass of solute + Mass of water")xx 100` `10 = (x)/((x + 100)) xx 100 or 1 = (x)/((x + 100)) xx 10` `x + 100 = 10x or 9x = 100 or x = (100)/(9) = 9.1 g` |
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| 11. |
Sodium chloride contains two elements, but it is still a pure substance. Assign reason. |
| Answer» The two elements sodium and chlorine have combined with each other by chemical reaction to form sodium chloride (NaCl) which is a chemical compound. Since these elements cannot be separated from each other be any physical process, sodium chloride is a pure substance. | |
| 12. |
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. |
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Answer» Pure substances are: Ice, Calcium oxide and Mercury. (Note. Hydrochloride acid is a mixture of hydrogen chloride gas and water, so it is not a pure substance). |
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| 13. |
Explain the following given examples: `{:((a),"saturated solution",(b)"pure substance"),((c ),"colloid",(d)"suspension"):}` |
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Answer» (a) Saturated solution. A solution in which on more solute can be dissolved at that temperature, is called a saturated solution. For example, if in an aqueous salt solution, no more salt can be dissolved at that temperature, than that salt solution will be a saturated solution. Thus, a saurated solution contains the maximum amount of solute whihc can be dissolved in it at that temperature. For example, a maximum of 36 grams of sodium chlorede (common salt) can be dissolved in 100 grams of water at `20^(@)C,` so a saturated solution of sodium chloride at `20^(@)C` contains 36 grams of sodium chloride dissolved in 100 grams of water. (b) Pure substance. See Q. No. 1 on pages 225 of this book. (c ) Colloid. A colloid is a kind of solution in which the size of solute particles is intermediate between those in true solutions and those in suspension. The size of solute particles in a colloid is bigger than the of a true solution but smaller than those of a supernsion. Though colloids appear to be homogeneous to us but actually they are found to be hetergeneous when observed through a high power microscope. So, a colloid is not a true solution. Some of the examples of colloids (or colloidal solutions) are: Sope solution, starch solution, Milk, Ink, Blood, Jelly and solutions of synthetic detergents. Colloids are also known as colloidal solutions. (d) Suspension. A suspension is a hetergeneous mixture in which the small particles of a solid are spread throughout a liquid without siddolving in it. Some common example of suspension are: Chalk-water mixture, Muddy water, Milk of Magnesia Sand particles suspended in water, and Flour in water. Chalk-water mixture is suspensinon of fine chalk particles in water, muddy water is a suspension of soil particles in water, and milk of Magnesia is a suspension of magnesium hydroxide in water. Please note that solid particles and water remain separate in a suspension. The particles do not dissolve in water. |
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| 14. |
Which of the following statements are true for pure substances ? (i) Pure substances contain only one kind of particles (ii) Pure substances may be compounds or mixtures (iii) Pure substances have the same composition throughout (iv) Pure substances can be exemplified by all elements other than nickel.A. (i) and (ii)B. (i) and (iii)C. (iii) and (iv)D. (ii) and (iii). |
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Answer» Correct Answer - B Both these statements are correct. |
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| 15. |
Point out whether the following statements are true or false : (i) Particles in a colloidal solution can always be seen by naked eyes. (ii) Scattering of light occurs when a beam of liquid is passed through aqueous sugar solution. (iii) Colloidal solutions are of heterogeneous nature. (iv) Digestion of food is a chemical change. |
| Answer» (i) False (ii) False (iii) True (iv) True. | |
| 16. |
(a) Classify Brass and Diamond as element and mixture. (b) How is a chemical change different from a physical change ? |
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Answer» (a) Brass is a homogeneous mixture also called alloy. The constituents are Cu and Zn. Diamond is an element. It is an allotropic form of carbon. (b) In a chemical change, a new substance is formed as a result of chemical reaction. No new substanceis formed in a physical change. |
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| 17. |
What types of mixtures are represented by the following ? (a) Carbon dioxide gas dissolved in water. (b) Air containing suspended particles. (c ) Soap bubbles formed by blowing air into soap solution. |
| Answer» (a) homogeneous (b) heterogeneous (c ) heterogeneous. | |
| 18. |
Which of the the following statements are true for pure substance ? (i) pure substance contain only one kind of particles (ii) pure substance may be compounds or mixtures(ii) pure substance have the same composition throughout (iv) pure substances can be exemplified by all elements other than nickelA. (i) and (ii)B. (i) and (iii)C. (iii) and (iv)D. (ii) and (iii) |
| Answer» Correct Answer - ( b) | |
| 19. |
Why does a salt disappear when dissolved in water ? |
| Answer» Water helps in separating ions from a salt. The interionic forces decrease and the ions get dispersed. Therefore, salt dissolves in water and disappears. | |
| 20. |
Identify the colloids from the following : Soda water, milk, sponge, clouds, mixture of alcohol and water, jelly. |
| Answer» Colloids : Soda water, milk, sponge, clouds, jelly. | |
| 21. |
(a) Enumerate any two differences between simple distillation and fractional distillation. (b) Draw a labelled diagram showing the process of fractional distillation. |
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Answer» (a) (i) Simple distillation can be used if the liquids to be separated differ in their boiling points by more than `25^(@)C`. If the difference is less, than fractional distillation can be used. (ii) A fractionating column is needed for fractional distillation but not for simple distillation. (b) For process of fractional distillation. |
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| 22. |
state one instance where water undergoes a physical change and one in which it which it undergoes a chemical change . |
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Answer» Physical change : Evaporation of water or freezing of water Chemical change : Electrolysis of water. |
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| 23. |
Why particles in a true solution cannot be seen with a naked eye ? |
| Answer» Particle size in a true solution is less than `10^(-9)` m or 1 nm. The particles are too small to scatter the beam of light and therefore, cannot be seen with naked eye. | |
| 24. |
When a solution is said to be saturated ? How can you change a saturated solution to an unsaturated solution without adding any more solvent to it ? Explain in brief. |
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Answer» A solution is said to be saturated if it has the maximum amount of the solute dissolved in a given amount of the solvent at a given temperature. Saturated solution can also be made unsaturated by increasing the temperature provided the process of dissolution of the solid solute is of endothermic nature i.e., it is accompanied by the absorption of heart. |
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| 25. |
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ? |
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Answer» Volume percent = `("Volume of solute(alcohol)")/("Volume of solution")` `12% or (12)/(100) = ((12 mL))/("Volume of solution")` or volume of solution = 100 mL or Volume of water to be added = (100 - 12) = 88 mL |
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| 26. |
Process of simple distillation can be used to separate the constituents from a liquid mixture differing the their boiling points by `25^(@)C` or more. However, fractional distillation is effective if the difference in boiling points is less than `25^(@)C`. How will you explain this ? |
| Answer» In simple distillation, only the low boiling liquid will distil while high boiling liquid will remain in the distillation flask. Thus, separation can be done if the difference in the boiling points of the liquids is `25^(@)C` or more. In the second case, both the liquids will distil simultaneously. The distillate will contain the fractions of both the liquids. If a fractionating column is used, the vapours of high boiling liquid will also rise into the column along with the low boiling liquid. But they will condense first releasing energy (called latent heat of condensation) and fall back in the distillation flask as a liquid. This energy will be absorbed by the vapours of the low boiling liquid which will remain in the vapour state. It will get distilled while the high boiling liquid unable to get distilled, remain in the distillation flask only. In this way, separation can be done. Thus, the role of fractionating column is to put obstructions in the path of the vapours of the liquids that are rising upwards. | |
| 27. |
Differentiate between simple distillation and fractional distillation. |
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Answer» (a) In fractional distillation, a fractionating column is used while no such column is needed in simple distillation. (b) Simple distillation can be used to separate two miscible liquids differing in their boiling points by more than `25^(@)C`. In case, the difference is less than this, fractional distillation is used. |
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| 28. |
(a) Identify the solute and solvent in tincture of iodine. (b) Why is Tyndall effect not seen in a true solution ? |
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Answer» (a) In tincture of iodine, solute present is iodine and solvent is ethyl alcohol. (b) In a true solution, the particle size is so small that it does not scatter the beam of light. Therefore, Tyndall effect is not seen in a true solution. |
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| 29. |
State which of the following solutions exhibit Tyndall effect : Starch solution, Sodium chloride solution, Tincture of iodine, Air. |
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Answer» (i) Tyndall effect is shown both by starch solution and air which are heterogeneous mixtures and have the capacity to scatter beam of light as it passes through them. (ii) Sodium chloride solution and tincture of iodine (iodine crystals dissolved in thyl alcohol) are both homogeneous in nature and donot exhibit any Tyndall effect. |
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| 30. |
(a) All mixtures are homogeneous. Is this statement correct ? Justify your answer. (b) How can a saturated solution be made unsaturated ? |
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Answer» (a) No, this statement is wrong. Mixtures can be homogeneous only if the constituents present are uniformly mixed and there is no boundary of separation of these constituents. (b) A saturated solution can be made unsaturated in two ways : (i) By increasing the temperature or by heating (ii) By adding more of the solvent or by diluting the solution. |
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| 31. |
(a) Name a metal which is liquid at room temperature. (b) Smoke and fod are aerosols. How do they differ from each other ? (c ) Name an element which melts when kept on the palm. |
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Answer» (a) Metal is mercury (Hg). (b) In smoke, dispersed phase is a solid (dust or carbon particles). In aerosols, it is a liquid (water drops). Dispersion medium in both the cases is the same i.e. air. (c ) It is either gallium (Ga) or cesium (Cs). |
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| 32. |
List the two conditions essential for using distillation as a method for separation of the components from a mixture. |
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Answer» (i) The components of the mixture must be miscible with each other. (ii) In case, both the miscible components are liquids, they must differ in their boiling point by more than `25^(@)C`. |
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| 33. |
You are given a mixture of iodine in alcohol caled tincture iodine. Which method will you use to recover both, iodine as well as alcohol, from this mixture?A. evaporationB. simple disillationC. fractional distillationD. crystallisation |
| Answer» Correct Answer - (b) | |
| 34. |
(a) Name a non-metallic element found in (i) liquid state (ii) gaseous state. (b) Pick metalloid from the elements carbon, silicon, phophorus, gold. (c ) Which two properties of metals enable us to give the desired shapes to metals ? |
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Answer» (a) (i) Bromine `(Br_(2))` (ii) Oxygen `(O_(2))`. (b) Silicon (Si) is a metalloid (c ) Metals are melleable and ductile. i.e., they can be beaten into sheets and drawn into wires. |
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| 35. |
One of the following does not undertgo sublimation. This one is:A. camphorB. dry iceC. silicaD. iodine |
| Answer» Correct Answer - (c ) | |
| 36. |
The best way to recover sugar from an aqueous sugar solution is:A. evaporation to drynessB. distillationC. filtrationD. crystallisation |
| Answer» Correct Answer - (d) | |
| 37. |
Which one of the following scrap metal cannot be separated by magnetic separation ?A. nickelB. cobaltC. chromiumD. steel |
| Answer» Correct Answer - (c ) | |
| 38. |
which one of the following is not a metalloid?A. BoronB. siliconC. galliumD. germanium |
| Answer» Correct Answer - ( c) | |
| 39. |
the element which is not common between the compounds called baking soda and soda ash isA. sodiumB. hydrogenC. oxgenD. carbon |
| Answer» Correct Answer - ( b) | |
| 40. |
Name two metals which are both malleable and ductile. |
| Answer» Copper and silver are both malleable and ductile. | |
| 41. |
"Is malleable and ductile " best describes:A. a solutionB. a metalC. a compoundD. a non - metal |
| Answer» Correct Answer - (b) | |
| 42. |
An elements is sonorous and highly ductile. Under which category would you classify this element ? What other characteristics do you expect the element to possess ? |
| Answer» The element is a metal, It is expected to possess the important characteristics of the metals. | |
| 43. |
Describe a method of separating common salt from a mixture of common salt and chalk powder. |
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Answer» this mixture cntains two constituents : common salt and chalk powder ,Now , common salt is soluble in water ehereas chalk powder is insoluble in water ,SO ,this difference in their solubility will be used to separate them , this is done as follows : (i) Some water is added to the mixture of common salt and chalk powder ,and stirred ,Common salt dissolves in water to from salt solution whereas chalk powder remains undissolved . (ii) On filtering , chalk powder is obtained as a residue on the fiter paper and salt solution is obtanied as filtrate . (iii) the salt solution (filtrate ) is evaporated to dryness when common salt is left behind. |
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| 44. |
Arun has prepared 0301% (by mass) solution of sodium chloride in water. Which of the following correctly represents the composition of the solution ? (a) 1.00 g of NaCl + 100 g of water (b) 0.11 g of NaCl + 100 g of water (c ) 0.01 g of Nacl + 99.99 g of water (d) 0.10 g of NaCl + 99.90 g of water. |
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Answer» By definition 0.01% (by mass) solution means that 0.01 g of sodium chloride is dissolved in 0.99 g (by mass) of water. Therefore (c ) represents the correct composition of the solution. This can be further verified as follows : Mass percent = `("Mass of sodium chloride")/("Mass of solution")xx 100` `=((0.01g))/((0.99 + 0.01))xx 100 =0.01%` |
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| 45. |
How will you justify that water is a compound ? |
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Answer» Water is considered to be a compound due to the following reasons : (i) Water cannot be separated into its constituents hydrogen and oxygen by physical methods. (ii) Properties of water are entirely different from its constituents hydrogen and and oxygen. Hydrogen is combustible while oxygen supports combustion. Water is quite different from the two and it extinguishes fire. (iii) Heat and light are given out when water is formed by burning hydrogen and oxygen. (iv) The composition of water is fixed. Its constituents hydrogen and oxygen are present in the ratio of 1 : 8 by mass. (v) Water has a fixed boiling point of `100^(@)C` (or 373 K) under atmospheric pressure of one atmosphere (or 760 mm). |
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| 46. |
Classify the following as physical or chemical properties (a) The composition of a sample of steel is : 98% iron. 1.5% carbon and 0.5% other elements. (b) Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas. (c ) Metallic sodium is soft enough to be cut with a knife. (d) Most metal oxides form alkalis on interacting with water. |
| Answer» (a) Physical (b) Chemical (c ) Physical (d) Chemical. | |
| 47. |
During an experiment the students were asked to prepare a 10% (Mass/Mass) solution of sugar in water. Ramesh dissolved 10g of sugar in 100g of water while Sarika prepared it by dissolving 10g of sugar in water to make 100g of the solution. (a) Are the two solutions of the same concentration (b) Compare the mass % of the two solutions. |
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Answer» (a) No, the two solutions have different concentrations. (b) Mass % of solution prepared by Ramesh = `("Mass of sugar")/("Mass of solution")xx 100` `=(10)/((10 + 100)) xx 100 = (10)/(110) xx 100 = 9.09%` Mass % of solution prepared by Sarika = `("Mass of sugar")/("Mass of solution")xx 100 = (10)/(100) xx 100 = 10.0%` |
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| 48. |
Which of the following are chemical changes ? (i) Decaying of wood (ii) Burning of wood (iii) Growth of wood in a tree (iv) Hammering of a nail on a piece of wood.A. (i) and (ii)B. (ii) and (iv)C. (iii) and (iv)D. (i), (ii) (iii). |
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Answer» Correct Answer - D All the three are chemical changes. |
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| 49. |
which of the following are chemical change ?(i) decaying of wood (ii) burning of wood (iii) sawing of wood (iv) hammering of nail into woodA. (i) and (ii)B. (ii) and (iii)C. (iii) and (iv)D. (i) and (iv) |
| Answer» Correct Answer - (a) | |
| 50. |
state three reasons why you think air is a mixture and water is a compound. |
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Answer» The justification can be done on the basis of the following points in its supports. 1. The composition of air is not always the same. At high altitudes, the percentage of oxygen decreases. Similarly, in industrial towns, we normally say that the air is more polluted. This means that the percentages of carbon monoxide, sulphur dioxide and other poisonous gases in air has increased. 2. The major constituents of air can be easily separated by physical methods such as liquefaction, fractional distillation etc. We shall discuss these methods a little later in the present chapter. 3. The different gases present in air do not lose their identities. For example, air supports combustion which means that it contains oxygen. Similarly, air turns lime water milky. This establishes the presence of carbon dioxide in air. 4. No energy changes or no chemical reactions occur when the constituents of air are tried to be mixed. All these evidences support the fact that air is a mixture and not a compound. |
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