A colloid is a ______ mixture and its components can be separated by the technique known as ______.
Answer: A colloid is a heterogeneous mixture and its components can be separated by the technique known as centrifugation. Colloids... View Article
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Give an example each for the mixture having the following characteristics. Suggest a suitable method to separate the components of these mixtures (a) A volatile and a non-volatile component. (b) Two volatile components with appreciable difference in boiling points. (c) Two immiscible liquids. (d) One of the components changes directly from solid to gaseous state. (e) Two or more coloured constituents soluble in some solvent.
Answer: (a) Mixture of acetone and water. It can be separated by distillation. (b) Mixture of petrol and kerosene. Can... View Article
An element is sonorous and highly ductile. Under which category would you classify this element? What other characteristics do you expect the element to possess?
Answer: An element which is sonorous and highly ductile can be classified as metal. Metals Metals are minerals or substances... View Article
What are the favourable qualities given to gold when it is alloyed with copper or silver for the purpose of making ornaments?
Answer: Pure gold that is 24 karats is soft and does not have strength. In order to give strength to... View Article
You are given two samples of water labelled as ‘A’ and ‘B’. Sample ‘A’ boils at 100°C and sample ‘B’ boils at 102°C. Which sample of water will not freeze at 0°C? Comment.
Answer: Sample B may consist of impurities. At 1 atm the boiling point of water is 100°C and freezing point... View Article
Name the process associated with the following (a) Dry ice is kept at room temperature and at one atmospheric pressure. (b) A drop of ink placed on the surface of water contained in a glass spreads throughout the water. (c) A potassium permanganate crystal is in a beaker and water is poured into the beaker with stirring. (d) An acetone bottle is left open and the bottle becomes empty. (e) Milk is churned to separate cream from it. (f) Settling of sand when a mixture of sand and water is left undisturbed for some time. (g) Fine beam of light entering through a small hole in a dark room, illuminates the particles in its paths
Answer: (a) Dry ice is kept at room temperature and at one atmospheric pressure – Sublimation (b) A drop of... View Article
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: Most of the substances that we see around have certain characteristics and properties by which they can be classified... View Article
Explain why particles of a colloidal solution do not settle down when left undisturbed, while in the case of a suspension they do.
Answer: The size of colloidal particles is smaller. They continue to move in a zig-zag pattern, avoiding the force of... View Article
What would you observe when (a) a saturated solution of potassium chloride prepared at 60°C is allowed to cool to room temperature. (b) an aqueous sugar solution is heated to dryness. (c) a mixture of iron filings and sulphur powder is heated strongly.
Answer: (a) Sodium potassium chloride will separate out from the saturated solution when the temperature of the solution reduced from... View Article
While diluting a solution of salt in water, a student by mistake added acetone (boiling point 56°C). What technique can be employed to get back the acetone? Justify your choice.
Answer: Fractional Distillation can be used to separate acetone from the mixture of salt and water. There are considerable differences... View Article
The ‘sea-water’ can be classified as a homogeneous as well as heterogeneous mixture. Comment.
Answer: Mixtures are formed when two or more substances (elements or compounds) mix together without participating in a chemical change.... View Article
Salt can be recovered from its solution by evaporation. Suggest some other technique for the same?
Answer: The other method used to recover the salt from its solution is crystallization. Crystallization is a more efficient process as it... View Article
Which of the tubes in Fig. (a) and (b) will be more effective as a condenser in the distillation apparatus?
Answer: Beads in tube (A) provide an increased surface area for cooling of the vapours that come in contact with... View Article
Suggest separation technique(s) one would need to employ to separate the given mixture – Kerosene oil, water and salt
Answer: Immiscible layers separate out in layers depending on their densities in separating funnel. Separation techniques of Kerosene oil and... View Article
Suggest separation technique(s) one would need to employ to separate the given mixture – Common salt, water and sand
Answer: (i) Because common salt is soluble in water but sand is not, the decantation (or filtration) technique is used... View Article
Suggest separation technique(s) one would need to employ to separate the given mixture – Potassium chloride and ammonium chloride
Answer: Potassium chloride and ammonium chloride are separated by sublimation method because ammonium chloride being a sublimate, sublimes leaving behind... View Article
Suggest separation technique(s) one would need to employ to separate the given mixture – Mercury and water
Answer: Decantation method is used to separate the mixture of Mercury and water. Here Mercury is heavier than water hence... View Article
Two chemical species X and Y combine together to form a product P which contains both X and Y X + Y → P. X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species X, Y and P are correct? (i) P is a compound (ii) X and Y are compounds (iii) X and Y are elements (iv) P has a fixed composition (a) (i), (ii) and (iii), (b) (i), (ii) and (iv) (c) (ii), (iii) and (iv) (d) (i), (iii) and (iv)
Answer: (d) (i), (iii) and (iv) X + Y → P X and Y cannot be further broken down into... View Article
Two substances, A and B were made to react to form a third substance, A2B according to the following reaction 2A + B → A2B which of the following statements concerning this reaction are incorrect? (i) The product A2B shows the properties of substances A and B (ii) The product will always have a fixed composition (iii) The product so formed cannot be classified as a compound (iv) The product so formed is an element (a) (i), (ii) and (iii), (b) (ii), (iii) and (iv) (c) (i), (iii) and (iv) (d) (ii), (iii) and (iv)
Answer: (c) (i), (iii) and (iv) 2A + B → A2B A2B is a compound made up of two elements... View Article
Which of the following are chemical changes? (i) Decaying of wood (ii) Burning of wood (iii) Sawing of wood (iv) Hammering of a nail into a piece of wood (a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv)
Answer: (a) (i) and (ii) Decaying of wood and burning of wood, because there will be a change of chemical... View Article
