Science
Time Allowed: 3 Hours Maximum Marks: 80
General Instructions:
(i) All questions would be compulsory. However, an internal choice of approximately 33% would be provided. 50% marks are to be allotted to competency-based questions.
(ii) Section A would have 16 simple/complex MCQs and 04 Assertion-Reasoning type questions carrying 1 mark each.
(iii) Section B would have 6 Short Answer (SA) type questions carrying 02 marks each.
(iv) Section C would have 7 Short Answer (SA) type questions carrying 03 marks each.
(v) Section D would have 3 Long Answer (LA) type questions carrying 05 marks each.
(vi) Section E would have 3 source based/case based/passage based/integrated units of assessment (04 marks each) with sub-parts of the values of 1/2/3 marks.
SECTION – A
Question I to 16 are multiple choice questions. Only one of the choices is comet. Select and write the correct choice as well as the answer to these questions.
1. An object at a distance of 30 cm from a concave mirror gets its image at the same point. The focal length of the mirror is
(a) – 30 cm
(b) 30 cm
(c) – 15 cm
(d) +15 cm
Ans. (c) – 15 cm
2. Which one of the following is the correct sequence of the components of a reflex arc?
(a) Muscles -> Receptors -> Sensory neuron -> Motor neuron -+ Spinal cord
(b) Spinal cord -> Motor neuron -> Sensory neuron -> Receptors -> Muscles
(c) Receptors –> Motor neuron -> Sensory neuron -> Spinal cord -> Muscles
(d) Receptors -> Sensory neuron -> Spinal cord -> Motor neuron -> Muscles
Ans. (d) Receptors -> Sensory neuron -> Spinal cord -> Motor neuron -> Muscles
3. The electronic configuration of four elements is given below:
P – 2, 8, 1; Q – 2, 4; R – 2, 8, 7; S – 2, 8
Which two elements will combine to form a covalent bond?
(a) P and Q
(b) Q and R
(c) R and S
(d) P and S
Ans. (b) Q and R
Covalent bonds are formed between non-metals. ‘P’ element is metal and ‘S’ is a noble gas.
4. The number of male gametes produced in each pollen grain is
(a) one
(b) two
(c) three
(d) four
Ans. (b) two
S. Ronit placed two resistors of 20 Ω and 30 Ω first in series and then in parallel with a 50 Ω resistor. What will be the effective resistance of the combination?
(a) 20 Ω
(b) 25 Ω
(c) 30 Ω
(d) 50 Ω
Ans. (b) 25 Ω
6. What will be name and molecular formula of the 4th member of the homologous series of carbon compounds which is represented by the general formula CnH2n+1OH?
(a) Butanol, C4H9OH
(b) Butanal, C4H120
(c) Pentanol, C5H110H
(d) Butanoic acid, C4H10OH
Ans. (a) Butanol, C4H9OH
7. A student performs a cross between two heterozygous tall pea plants and obtains 160 plants in F1 generation. What would be the number of tall and short plants in the F2 generation when she self pollinated the plants from F1 progeny?
Ans.
Out of 160, 120 would be tall and 40 would be dwarf
8. A current through a horizontal power line flows from South to North direction. The direction of magnetic field line above it is from
(a) North to South
(b) South to North
(c) West to East
(d) East to West
Ans. (d) East to West
Apply right-hand thumb rule. It is from East to West.
9. Which of the following metals liberate hydrogen gas with 5% HNO3?
(i) Cu (ii) Zn (iii) Mn (iv) Mg
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Ans. (c) (iii) and (iv)
10. Which of the given plants is/are raised by vegetative propagation method?
(i) Banana (ii) Pea
(iii) Gram (iv) Wheat
(v) Tomato (vi) Rose
Select the correct option.
(a) (i), (ii) and (v)
(b) (iii) and (vi)
(c) (iii) and (iv)
(d) (i) and (vi)
Ans. (d) (i) and (vi)
11. The components of peripheral nervous system is/are:
(a) Spinal nerves
(b) Cranial nerves
(c) Both spinal and mixed nerves
(d) Both spinal and cranial nerves
Ans. (d) Both spinal and cranial nerves
12. Nina’s grandmother is suffering from both myopia and hypermetropia. She needs a lens of power +4D for correcting her near vision and —5D for correcting her distant vision. Which of the following will be the ratio of the focal lengths of lenses required to correct these defects?
(a) 5 : 4
(b) 6 : 5
(c) 1: 1
(d) 3 : 4
Ans. (a) 5 : 4
13. In the given chemical reaction, alkaline potassium permanganate acts as
(a) a reducing agent
(b) an oxidising agent
(c) a dehydrating agent
(d) a redox agent
Ans. (b) an oxidising agent
14. Select the change that does not take place in a fertilized egg till the birth of the child in the human female reproductive system.
(a) Implantation of zygote in the inner uterine wall
(b) The inner lining of the uterus slowly breaks and comes out.
(c) Fertilised egg starts dividing
(d) Embryo changes to foetus.
Ans. (b) The inner lining of the uterus slowly breaks and comes out.
15. Commercial unit of electrical energy is kilowatt hour (kWh). Which of the following is/are true for kWh?
(i) 1 kWh = 1 unit of electric energy (ii) 1 kWh = 1 Ws-1
(iii) 1 kWh = 3.6 x 10-6J (iv) 1 kWh = 3.6 x 106J
(a) Only (ii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)
Ans. (c) (i) and (iv)
16. Which one of the following correctly represents calcium oxide?
Ans. Option (d)
Question No. 17 to 20 consist of two statements — Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below:
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
17. Assertion (A): Height in plants is genetically controlled.
Reason (R): Plants with more growth hormones being released grow taller than other plants.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans. (a) Both A and R are true, and R is the correct explanation of A.
18. Assertion (A): The value of refractive index for a given pair of media depends upon the speed of light in the two media.
Reason (R): Light travels fastest in vacuum with the highest speed of 3 x 108 ms-1.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans. (b) Both A and R are true, and R is not the correct explanation of A.
19. Assertion (A): If a pinch of baking soda is added to fresh milk, it takes more time to set as curd.
Reason (R): Baking soda decreases the pH value of fresh milk to below 6.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans. (c) A is true but R is false.
20. Assertion (A): Synapse is a microscopic gap present between two neurons.
Reason (R): In a synapse, chemical signal is transmitted from axonal end of one neuron to the dentritic end of another neuron.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, and R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans. (b) Both A and R are true, and R is not the correct explanation of A.
SECTION – B
Question No 21 to 26 are Very Short Answer Questions.
21. Mahak draws the following set up. Study it carefully and answer the following questions.
(a) What type of reaction takes place?
Ans. The type of reaction is electrolytic decomposition reaction.
(b) Why this is considered as an example of endothermic reaction?
Ans. This is considered an endothermic reaction as energy in the form of electrical energy is absorbed during the decomposition of water.
(c) Why is the amount of gas collected in one of the test tubes is double to the amount collected in the other?
Ans. Two volumes of hydrogen gas and one volume of oxygen gas are generated when water is electrolytically decomposed, i.e., ratio of hydrogen to oxygen is 2: 1 by volume.
(d) Write the balanced chemical equation for the same.
Ans. 2H2O(l) Electrolysis, 2H2 (g) + O2(g)
OR
A child dropped an iron nail into the solution of copper sulphate as shown in the given figure.
(a) State the colour changes observed by her.
Ans. Colour changes:
• Iron nail becomes brown in colour.
• Blue colour of copper sulphate solution fades and changes to light green.
(b) Why is/are the colour change take place?
Ans. Iron being more reactive displaces the copper from its solution. As a result blue colour of copper sulphate solution fades. Iron sulphate formed has light green colour. The displaced copper is deposited on the iron nail giving it a brownish colour.
(c) What type of reaction is it?
Ans. The type of reaction is single displacement reaction.
(d) Write the balanced chemical equation for the same.
Ans.
22. (a) What are chromosomes? How many pairs of chromosomes are present in human beings?
Ans. Chromosomes are thread like structures which are made up of proteins and DNA. 23 pairs of chromosomes are present in human beings.
(b) In an asexually reproducing organism, a trait ‘A’ exists in 10% of a population and trait S’ in 85% of the same population. Which of the two traits is likely to have arisen earlier? Give reason.
Ans. Trait ‘B’ which exists in 85% of the population is likely to have arisen earlier because in asexual reproduction identical copies of DNA are produced and variations do not arise. 85% of the population with trait ‘B’ must have been replicating that trait for a longer period of time than 10% of the population with trait ‘A’.
23. What is SI unit of electrical resistivity? Derive it mathematically. A wire has resistance R and length 1, if the length of the wire is doubled, what will be the change in resistivity and resistance of wire?
Ans. SI unit of electrical resistivity is ohm meter. We know
Resistivity of a material of wire will not change as it is a characteristic property of the material. If the length of the wire is doubled, resistance will also double as resistance is directly proportional to the length of the wire.
24. (a) Draw a labelled diagram to illustrate matter flow in a three step food chain.
Ans.
(b) Write any two methods of waste disposal which are practiced at your place.
Ans. Methods of waste disposal practiced at home
– Segregation
– Recycling
– Composting
25. A metal nitrate ‘X’ on heating gives a metal oxide along with evolution of a brown coloured gas rY’ and a colourless gas ‘Z’, which helps in burning.
(a) Identify ‘X’, ‘Y” and ‘Z’.
Ans.
(b) Name the type of reaction and write a balanced chemical equation.
Ans. The type of reaction is thermal decomposition reaction.
26. Neha wants to obtain an equal sized, real and inverted image of an object on a screen.
(a) What type of lens should she use?
Ans. Convex lens
(b) Where would be the image formed?
Ans. Object should be placed at centre of curvature or 2F of convex lens, i.e., u = 2f to obtain, real and equal size inverted image at 2F, i.e., v = 2f on the other side of the lens.
(c) Draw a ray diagram to show the formation of the image.
Ans.
Or
(a) Define principal focus of a mirror.
Ans. It is a point on the principal axis at which all the incident rays parallel to the principal axis meet after reflection from a concave mirror or appear to meet in case of convex mirror.
(b) Draw ray diagrams when
(i) object is placed between principal focus and pole in case of concave mirror.
Ans.
(ii) object is placed at infinity in case of the concave lens.
Ans.
SECTION – C
Question No. 27 to 33 are Short Answer Questions.
27. (a) Name the substance oxidised and reduced in the given reaction.
Ans.
(b) State two effects of oxidation reactions in everyday life.
Ans. Effects of oxidation reactions in everyday life.
– Corrosion
– Rancidity
(c) ‘Translate the following statement into chemical equation and then balance it.
Barium chloride solution reacts with aluminium sulphate solution to give aluminium chloride solution and precipitate of barium sulphate.
Ans.
28. Study the given diagram and answer the following questions.
(a) Identify A and B.
Ans. A – Liver
B – Pancreas
(b) Name the secretion/s that is/are released by A and B. Also write the functions of these secretions.
Ans. Part A (Liver) secretes bile juice and bile salts which is stored in gall bladder.
• Bile juice makes the acidic food alkaline to facilitate the action of enzymes on it.
• Bile salts breakdown fats present in food into small globules which is also called emulsification.
Part B (Pancreas) secretes pancreatic juice which contain enzymes. Enzymes are trypsin and lipase.
• Trypsin helps to digest proteins into amino acids.
•Lipase breaks down emulsified fats into smaller globules.
OR
Study the given diagram showing schematic plan of blood circulation and answer the following questions.
(a) Label (i), (ii), (iii), (iv) and (v)
Ans. (i) – Capillaries in body organs
(ii) – Vena cava from body
(iii) – Aorta
(iv) Pulmonary vein from lungs
(v) Pulmonary artery to lungs
(b) Write the function of part marked (v).
Ans. Pulmonary artery takes deoxygenated (impure) blood from right atrium to lungs for purification.
29. (a) What is a trophic level? Why are producers considered to be at the first trophic level of all food chains?
Ans. Each step or level of the food chain forms a trophic level. Producers are considered to be at the first trophic level of all food chains as they manufacture their own food by the process of photosynthesis using energy from the sun.
(b) How is energy lost from the trophic levels in an ecosystem?
Ans. The ways by which energy is lost from the trophic levels in an ecosystem are:
• as heat to the environment
• utilised in growth and reproduction
• in maintaining life process like nutrition.
• in doing work
(c) List the components of an ecosystem.
Ans. The components of an ecosystem are:
• abiotic components (non-living components)
• biotic components (living components)
30. (a) How will the focal length of a mirror change when ‘u’ (object distance) is changed by moving the object towards or away from the mirror?
Ans. Focal length of a mirror does not depend upon object or image distance. It cannot be changed by moving the object towards or away from the mirror. Focal length can only change if radius of curvature of the mirror is changed as focal length is half of the radius of curvature i.e., f = R/2
(b) A concave mirror produces a real image 6 cm tall of an object 2 cm tall placed at 10 cm from the mirror. Calculate the focal length of the mirror and the position of the image.
Ans.
31. (a) Explain feedback mechanism by taking the example of insulin.
Ans. Hormones are secreted in extremely less quantities. Excess or deficiency of such hormones can have harmful effects on our body. A feedback mechanism controls the timing and secretion of hormones released by various glands.
For example: On the rise of blood glucose level, information is sent to pancreas to release insulin.
When the appropriate amount of glucose level is obtained in the blood, the release of insulin is stopped.
(b) What are receptors and where are they present in our body? Mention any two receptors present in our body and their functions.
Ans. Receptor is a cell or group of cells specialised to detect a particular stimulus and to initiate the transmission of impulses via sensory nerves. They are present on sense organs in our body. Gustatory receptors: They detect taste and are present on the tongue.
Olfactory receptors: They detect smell and are present in the nose.
32. (a) Which type of hydrocarbons burn with yellow smoky flame? Why?
Ans. Unsaturated hydrocarbons burn with yellow smoky flame due to presence of higher percentage of carbon.
(b) Write the molecular formula of an alkyne containing 10 atoms of hydrogen.
Ans.
33 (a) Four resistors, each of 15 Ω resistances are connected to form a square PQRS as shown in the figure.
Calculate the resistance between the opposite corners P and R.
Ans. Between the opposite corners P and R
Resistance in the path PSR = 15 + 15 = 30 Ω
Resistance in the path PQR = 15 + 15 = 30 Ω
We know the resistance in the paths PSR and PQR are in parallel,
Resistance between P and R
The resistance between the opposite corners P and R is 15 Ω
(b) List the factors which affect the resistance of a conductor.
Ans. Resistance of the conductor depends
(i) on its length
(ii) on its area of cross-section
(iii) on the nature of its material
SECTION – D
Question No. 34 to 36 are Long Answer Questions.
34. (a) Which acid is left in the skin when a bee stings a person? What should be done to get immediate relief?
Ans. When a bee stings a person, it leaves formic acid (methanoic acid) in the skin which causes pain and irritation. Use of a mild base like baking soda on the stung area gives relief as base neutralises the acid.
(b) List two acids which are present in our eatables. Also state where they are used.
Ans. Tartaric acid is an ingredient of baking powder. It is used in making the cake soft, spongy and fluffy.
5-8% solution of acetic acid in water is called vinegar. It is used widely as a preservative in pickles.
(c) A small amount of an acid is produced in our stomach. Is it harmful or useful and in what way? If excess of acid is produced in the stomach, what should we do?
Ans. A small amount of hydrochloric acid is produced in the stomach which is useful as it can kill the harmful bacteria that may enter into the stomach along with the food. If excess of acid is produced, there is irritation and burning sensation in the stomach. To get relief, we can take antacid like milk of magnesia [Mg(OH)2] which neutralises the excess of acid.
Or
(a) Anita wants to know why the colour of copper sulphate crystals changes when they are heated. What is the colour change that takes place? Explain. Name one more salt where colour changes occur upon heating.
Ans. Copper sulphate crystals contain water of crystallisation. Water of crystallisation is the fixed number of water molecules present in one formula unit of copper sulphate. Chemical formula of salt is CuSO4.5H2O and colour is blue before heating. After heating, the colour of crystals changes to white and five molecules of water are removed.
Examples of salt having water of crystallisation
Iron sulphate – FeSO4.7H2O
The colour changes from green to dull white due to loss of 7 molecules of water of crystallisation. Then it changes to brownish black due to the formation of Fe2O3
(b) Study the figure carefully and answer the following questions.
(i) What can you conclude from this figure?
Ans. Acids conduct electricity as the bulb glows in acid solution. Acids dissociate in the solution to produce H+ (aq) ions, these H+ ions are responsible for the acidic properties and the electric current is carried through the ions.
(ii) If in place of dilute HCl, glucose solution is taken as an electrolyte, does the bulb glow? Explain.
Ans. If in place of dilute HCl, glucose solution is taken as an electrolyte, the bulb does not glow. It means the glucose solution does not dissociate and forms H+ as ions which are responsible for the conduction of electricity.
(iii) What happens when a base ‘X’ is dissolved in water? When solution of ‘X’ is taken as an electrolyte, does the bulb glow?
Ans. When a base ‘X’ is dissolved in water, it forms alkali solution of base ‘X’. When electricity is passed through solution of ‘X’, the bulb glows indicating the ions are formed in the solution due to the dissociation of alkali. When a base is dissolved in water, it generates (OH) ions in water and ions are responsible for conduction of electricity.
For Example
35.
(a) Identify the processes shown in ‘A’ and ‘B’.
Ans. A – Binary fission
B – Multiple fission
(b) Which organism uses method ‘A’ for reproduction? Name two more organisms which reproduces by this method.
Ans. Amoeba uses binary fission to reproduce. Examples of two more organisms which reproduce by binary fission are Paramecium and Leishmania.
(c) Differentiate between the processes ‘A’ and ‘B’.
Ans. Differences between binary fission and multiple fission
(d) Draw well labelled diagrams to show reproduction in the organism which causes sleeping sickness.
Ans. Sleeping sickness is caused by Leishmania
Or
(a) Label the parts marked as A, B, C and D.
Ans.
A – Pollen grain
B – Pollen tube
C – Male germ cell
D – Female germ cell
(b) What is the significance of part marked as B?
Ans. Part B is pollen tube that helps in transportation of male gamete to ovary.
(c) What happens to the part A if it falls on a compatible stigma?
Ans. Part A is pollen grain. When it falls on a suitable stigma, it starts germinating and forms a pollen tube. The pollen tube grows into the style and reaches the ovule. In the pollen tube the male nucleus divides into two male germ cells. The pollen tube then reaches the embryo sac into which it releases the two male gametes contained in it. One of the male gametes fuses with the female gamete.
(d) What happens when part marked as C fuses with D?
Ans. Part C is male germ cell and D is female germ cell. The male germ cell fuses with the female germ cell in the ovary and forms a zygote. The zygote divides several times to form an embryo within the ovule. The ovule develops a rough coat and is gradually converted into a seed. The ovary grows rapidly and ripens to form a fruit.
36. (a) The following current time graphs from two different sources have been drawn by a child.
(i) What type of current has been shown in the two cases?
Ans. (i) A – Direct current
B – Alternating current
(ii) Write differences between two types of currents shown in the graphs.
Ans. Differences between Direct current (DC) and Alternating current (AC)
(iii) Identify one source each for the currents shown in the graphs.
Ans. Source of direct current (DC) – Cell, battery, solar cell, DC generator
Source of alternating current (AC) – AC generator
(b) Define the following:
(i) Magnetic field
Ans. The space around a magnet in which the force of attraction and repulsion due to magnet can be detected is called the magnetic field.
(ii) Magnetic field lines.
Ans. The curved paths along which the iron filings arrange themselves due to forces acting on them in the magnetic field of the bar magnet are called magnetic field lines.
(c) Why don’t two magnetic field lines intersect each other?
Ans. If two magnetic field lines intersect each other at a point, the point will have two directions which is not possible.
Or
(a) What are the differences between a bar magnet and a solenoid?
Ans. A bar magnet is a permanent magnet and its polarity is fixed whereas a solenoid is a temporary magnet and its polarity is not fixed.
(b) What is an electromagnet? List any one use of it.
Ans. An electromagnet is a magnet consisting of a long coil of insulated copper wire wrapped around a soft iron core that is magnetised only when electric current is passed through the coil. Uses of electromagnet
(i) It is used to separate magnetic substance from non-magnetic substance.
(ii) It is used in electric bells, telephone receivers, microphones, loudspeakers, television etc.
(c) Draw a diagram to show the formation of an electromagnet.
Ans.
(d) What is the purpose of soft iron core used in making an electromagnet?
Ans. (i) Soft iron core makes the magnetic field stronger because it becomes a magnet itself.
(ii) Soft iron loses its magnetism as soon as the current stops flowing. So, it is a temporary magnet.
(e) What are the different ways of increasing the strength of an electromagnet?
Ans. (e) The strength of the electromagnet can be increased by
- increasing the number of turns in the coil as the strength is directly proportional to the number of turns.
- increasing the current in the coil as strength of electromagnet is directly proportional to the current flowing through it.
SECTION – E
Question No 37 to 39 are case-based/data-based questions.
37. The table below shows the hints given by the quiz master in a quiz. The parts A, B, C and D are labelled in the given figure.
Based on the above hints, answer the following questions:
(a) Identify A, B, C and D from the given figure.
Ans. A – Branch of renal artery
B – Glomerulus
C- Tubular part of nephron
D – Collecting duct
Attempt either subpart (b) or (c)
(b) (i) List two nitrogenous products which are removed from blood in the kidneys.
Ans. Urea and uric acid are the two nitrogenous wastes which are removed from blood in the kidneys.
(ii) List two parameters that decide the amount of water that is reabsorbed in the kidney. Or
Ans. The amount of water reabsorbed depends on:
– how much excess water there is in the body.
– how much of dissolved waste is to be removed.
(c) List the steps involved in urine formation.
Ans. (c) Steps involved in urine formation:
- Glomerular filtration: Nitrogenous wastes, glucose, water, amino acid filter from the blood into Bowman’s capsule of the nephron.
- Tubular reabsorption: Useful substances from the filtrate are reabsorbed back by capillaries surrounding the nephron.
– Secretion: Urea, extra water and salts are secreted into the tubule which open up into the collecting duct and then into the ureter.
38. The foundation of modern optics lays in 1672 when Sir Isaac Newton publishes his paper on the bending of light through prism. His experiments in bending of light through prisms led, eventually, to the revolutionary discovery of distinct coloured rays in white light and, distinguishable when refracted through a prism. In his experiment, he set up a prism near his window, and projected a beautiful spectrum 22 feet onto the far wall. Further, to prove that the prism was not colouring the light, he refracted the light back together by placing the second identical prism in an inverted position with respect to the first prism.
Attempt either subpart (a) or (b)
(a) How does the angle of minimum deviation of glass prism vary if the incident violet light is replaced by red light?
Ans. Among the seven colour components of white light, the red light has a higher wavelength and violet has the smaller wavelength. Again, angle of minimum deviation (D) is directly proportional to the refractive index (n), which, in turn, inversely proportional to the wavelength (λ) of light,
i.e.
Accordingly, deviation will decrease if the incident violet light is replaced by red light.
OR
(b) The refractive index of the material of the prism is √2 and angle of prism is 30°. One of the two refracting surfaces of the prism is made a mirror inward with a silver coating. At what angle of incidence, a beam of monochromatic light entering the prism from the other face will retrace its path (after reflection from the silvered surface)?
Ans.
(c) State the phenomenon of light used by the prism to form spectrum.
Ans. Dispersion of light
(d) What conclusion would you like to draw about angle of incident and angle of emergence in the case of refraction of light through a triangular glass prism?
Ans. The angle of emergence is almost equal to the angle of incidence.
39. Vinita draws the electrolytic refining of metal ‘X’ as shown below.
(a) (i) In the electrolytic refining of metal ‘X’, what would Vinita take as the anode, the cathode and the electrolyte?
Ans. Anode: Thick plate of impure metal ‘X’
Cathode: Thin plate of pure metal ‘X’
Electrolyte: Water soluble salt of metal ‘X’
(ii) Name two metals which can be refined electrolytically.
Ans. The metals which can be refined electrolytically are copper, zinc, tin, nickel, silver, gold etc.
Attempt either subpart (b) or (c)
(b) (i) What other name can be given to the following reaction other than thermit reaction?
Ans. Displacement reaction or exothermic reaction or aluminothermy.
(ii) Identify the substances that are getting oxidised and reduced in the above reaction.
Ans. Al is getting oxidised to Al2O3, Fe2O3, is getting reduced to Fe.
(iii) Where is thermit reaction used?
Ans. Thermit reaction is used to join railway tracks or cracked machine parts.
Or
(c) List the different steps used to extract mercury from its ore.
Ans. The ore of mercury is cinnabar.
The steps to extract mercury from its ore:
• Enrichment of ore
• Conversion of ore to oxide
• Reduction of metal oxide
• Refining of metal