The metals obtained from their molten chlorides by the process of electrolytic reduction are :
a.
Gold and silver
b.
Calcium and magnesium
Correct Answer
c.
Aluminium and silver
d.
Sodium and iron
Step-by-Step AI Explanation
Verified Method
Highly reactive metals like Na, Mg, Ca are extracted from their molten chlorides via electrolytic reduction because they have a high affinity for oxygen and cannot be reduced by carbon. Gold and silver are extracted differently, and iron is extracted by carbon reduction.
Q2mcq1 mark
The formation of magnesium oxide is correctly shown in option :
Step-by-Step AI Explanation
Verified Method
Magnesium (Mg) has an electronic configuration of 2, 8, 2. It loses 2 electrons to form Mg2+ (2, 8). Oxygen (O) has 2, 6 and gains 2 electrons to form O2- (2, 8). The correct representation shows the transfer of two electrons from Mg to O.
Q3mcq1 mark
Reaction between two elements A and B, forms a compound C. A loses electrons and B gains electrons. Which one of the following properties will not be shown by compound C ?
a.
It has high melting point.
b.
It is highly soluble in water.
c.
It has weak electrostatic forces of attraction between its oppositely charged ions.
Correct Answer
d.
It conducts electricity in its molten state or aqueous solution.
Step-by-Step AI Explanation
Verified Method
Compound C is an ionic compound. Ionic compounds are characterized by strong electrostatic forces of attraction, not weak ones. They possess high melting points, are soluble in water, and conduct electricity in aqueous or molten states.
Q4mcq1 mark
Consider the following reactions : (i) Dilute hydrochloric acid reacts with sodium hydroxide. (ii) Magnesium oxide reacts with dilute hydrochloric acid. (iii) Carbon dioxide reacts with sodium hydroxide. It is found that in each case :
a.
Salt and water is formed.
Correct Answer
b.
Neutral salts are formed.
c.
Hydrogen gas is formed.
d.
Acidic salts are formed.
Step-by-Step AI Explanation
Verified Method
These are all neutralisation-type reactions. (i) Acid + Base -> Salt + Water. (ii) Metal Oxide (basic) + Acid -> Salt + Water. (iii) Non-metal oxide (acidic) + Base -> Salt + Water. In every instance, water is a product alongside a salt.
Q5mcq1 mark
Tooth enamel is made up of calcium hydroxyapatite (a crystalline form of calcium phosphate). This chemical starts corroding in the mouth when the pH is :
a.
7
b.
5
Correct Answer
c.
10
d.
14
Step-by-Step AI Explanation
Verified Method
Tooth enamel is the hardest substance in the body but corrodes when the mouth pH falls below 5.5 due to acid production by bacteria breaking down leftover food particles.
Q6mcq1 mark
The products formed when Aluminium and Magnesium are burnt in the presence of air respectively are :
a.
Al3O4 and MgO2
b.
Al2O3 and MgO
Correct Answer
c.
Al3O4 and MgO
d.
Al2O3 and MgO2
Step-by-Step AI Explanation
Verified Method
Aluminium reacts with oxygen to form Aluminum oxide (Al2O3) and Magnesium reacts to form Magnesium oxide (MgO). These are the standard stable oxides for these metals in air.
Q7mcq1 mark
Electrolysis of water is a decomposition reaction. The mass ratio (MH : MO) of hydrogen and oxygen gases liberated at the electrodes during electrolysis of water is :
Step-by-Step AI Explanation
Verified Method
In the electrolysis of water (H2O), hydrogen and oxygen are produced in a 2:1 volume ratio. Since the molar mass of H2 is 2 and O2 is 32, the mass ratio is 2(2) : 1(32) = 4 : 32, which simplifies to 1:8.
Q8mcq1 mark
The breakdown of glucose has taken the following pathway : Glucose (a) ⎯⎯⎯→ Pyruvate + Energy (b) ⎯⎯⎯→ Lactic acid + Energy. The sites 'a' and 'b' respectively are :
a.
Mitochondria and Oxygen deficient muscle cells
b.
Cytoplasm and Oxygen rich muscle cells
c.
Cytoplasm and Yeast cells
d.
Cytoplasm and Oxygen deficient muscle cells
Correct Answer
Step-by-Step AI Explanation
Verified Method
Glucose is broken down to pyruvate in the cytoplasm (anaerobic). Pyruvate is then converted to lactic acid in muscle cells during strenuous exercise due to oxygen deficiency, or to ethanol/CO2 in yeast cells, or to CO2/H2O in mitochondria (aerobic).
Q9mcq1 mark
If pea plants with round and green seeds (RRyy) are crossed with pea plants having wrinkled and yellow seeds (rrYY), the seeds developed by the plants of F1 generation will be :
a.
50% round and green
b.
75% wrinkled and green
c.
100% round and yellow
Correct Answer
d.
75% wrinkled and yellow
Step-by-Step AI Explanation
Verified Method
In this dihybrid cross, Round (R) is dominant over Wrinkled (r), and Yellow (Y) is dominant over Green (y). The F1 generation inherits 'Ry' from the parent RRyy and 'rY' from rrYY, resulting in the genotype RrYy. Since R and Y are dominant, all F1 offspring will show the dominant phenotype: round and yellow seeds.
Q10mcq1 mark
The correct/true statement(s) for a bisexual flower is/are : (i) They possess both stamen and pistil. (ii) They possess either stamen or pistil. (iii) They exhibit either self-pollination or cross-pollination. (iv) They cannot produce fruits on their own.
a.
(i) only
b.
(iv) only
c.
(i) and (iii)
Correct Answer
d.
(i) and (iv)
Step-by-Step AI Explanation
Verified Method
A bisexual flower contains both the male (stamen) and female (pistil) reproductive parts. Because both parts are present, they are capable of self-pollination (pollination within the same flower) or cross-pollination. Option (ii) defines a unisexual flower, and (iv) is incorrect because bisexual flowers can definitely produce fruit.
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Which of the following groups do not constitute a food chain ? (i) Wolf, rabbit, grass, lion (ii) Plankton, man, grasshopper, fish (iii) Hawk, grass, snake, grasshopper, frog (iv) Grass, snake, wolf, tiger
a.
(i) and (iv)
b.
(i) and (iii)
c.
(ii) and (iii)
d.
(ii) and (iv)
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Mirror 'X' is used to concentrate sunlight in solar furnace and Mirror 'Y' is fitted on the side of the vehicle to see the traffic behind the driver. Which of the following statements are true for the two mirrors?
(i) The image formed by mirror 'X' is real, diminished and at its focus.
(ii) The image formed by mirror 'Y' is virtual, diminished and erect.
(iii) The image formed by mirror 'X' is virtual, diminished and erect.
(iv) The image formed by mirror 'Y' is real, diminished and at its focus.
a.
(i) and (ii)
b.
(ii) and (iii)
c.
(iii) and (iv)
d.
(i) and (iv)
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Assertion (A): The amount of ozone in the atmosphere began to drop sharply in the 1980s.
Reason (R): The oxygen atoms combine with molecular oxygen to form ozone.
a.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
b.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
c.
Assertion (A) is true, but Reason (R) is false.
d.
Assertion (A) is false, but Reason (R) is true.
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Assertion (A): No two magnetic field lines are found to cross each other.
Reason (R): The compass needle cannot point towards two directions at the point of intersection of two magnetic field lines.
a.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
b.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
c.
Assertion (A) is true, but Reason (R) is false.
d.
Assertion (A) is false, but Reason (R) is true.
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Assertion (A): A human child bears all the basic features of human beings.
Reason (R): It looks exactly like its parents, showing very little variations.
a.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
b.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
c.
Assertion (A) is true, but Reason (R) is false.
d.
Assertion (A) is false, but Reason (R) is true.
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Assertion (A): Decomposition reactions are generally endothermic reactions.
Reason (R): Decomposition of organic matter into compost is an exothermic process.
a.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
b.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
c.
Assertion (A) is true, but Reason (R) is false.
d.
Assertion (A) is false, but Reason (R) is true.
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An object is placed at a distance of 10 cm in front of a concave mirror of focal length 15 cm. Use mirror formula to determine the position of the image formed by this mirror.
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(a) Consider two lamps A and B of rating 50 W; 220 V and 25 W; 220 V respectively. Find the ratio of the resistances of the two lamps (i.e. RA : RB).
OR
(b) Heat produced per second due to a current in a resistor of 4 Ω is 400 joules. Calculate the potential difference across the resistor.
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(a) Besides minimising the loss of blood, why is it essential to plug any leak in a blood vessel? Name the component of blood which helps in this process and state how this component perform this function.
OR
(b) (i) The transport system in plants is relatively slower than in animals. Give reasons.
(ii) State the role of phloem in the transport of materials in plants.
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A student performs the following experiment in his school laboratory. List two observations to justify that in this experiment a chemical change has taken place.
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Translate the following statements into chemical equations and then balance them:
(a) Nitric acid reacts with calcium hydroxide to form calcium nitrate and water.
(b) Sodium chloride reacts with silver nitrate to form silver chloride and sodium nitrate.
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(a) Define one volt potential difference between two points in an electric field.
(b) Draw a schematic diagram of an electric circuit of a cell of 1·5 V, 5 Ω and 10 Ω resistor and a plug key, all connected in series. Calculate the current drawn from the cell when the key is closed.
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Consider the following electric circuit. Calculate the values of the following:
(a) The total resistance of the circuit
(b) The total current drawn from the source
(c) Potential difference across the parallel combination of 10Ω and 15Ω resistors
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Draw ray diagrams to show the nature, position and relative size of the image formed by a convex mirror when the object is placed (i) at infinity and (ii) between infinity and pole P of the mirror.
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(a) How many chromosomes are present in human beings? Out of these how many are sex chromosomes?
(b) Explain how, in sexually reproducing organisms, the number of chromosomes in the progeny is maintained.
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A hormone 'X' is secreted in blood when a person is under scary situation.
(a) Identify the hormone 'X' and the gland that secretes it.
(b) Explain its role in dealing with scary or emergency situations.
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(a) With the help of an activity, explain the conditions under which iron articles get rusted.
OR
(b) (i) Name two metals which react violently with cold water. List any three observations which a student notes when these metals are dropped in a beaker containing water.
(ii) Write a test to identify the gas evolved (if any) during the reaction of these metals with water.
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(a) ''Displacement reactions also play a key role in extracting metals in the middle of the reactivity series.'' Justify this statement with two examples.
(b) Why can metals high up in the reactivity series not be obtained by reduction of their oxides by carbon?
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(a) (i) The power of a lens 'X' is – 2·5 D. Name the lens and determine its focal length in cm. For which eye defect of vision will an optician prescribe this type of lens as a corrective lens ?
(ii) ''The value of magnification 'm' for a lens is – 2.'' Using new Cartesian Sign Convention and considering that an object is placed at a distance of 20 cm from the optical centre of this lens, state : (I) the nature of the image formed; (II) size of the image compared to the size of the object; (III) position of the image, and (IV) sign of the height of the image.
(iii) The numerical values of the focal lengths of two lenses A and B are 10 cm and 20 cm respectively. Which one of the two will show higher degree of convergence/divergence ? Give reason to justify your answer.
OR
(b) (i) Draw a ray diagram to show the refraction of a ray of light through a rectangular glass slab when it falls obliquely from air into glass.
(ii) State Snell's law of refraction of light.
(iii) Differentiate between the virtual images formed by a convex lens and a concave lens on the basis of : (I) object distance, and (II) magnification.
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(a) (i) Write the functions of the following parts of human female reproductive system : (I) Ovary (II) Fallopian tube (III) Uterus
(ii) State briefly two contraceptive methods used by human males.
OR
(b) (i) Differentiate between self-pollination and cross-pollination.
(ii) Identify A, B and C in the diagram given below and write one function of each.
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(a) (i) Draw electron dot structure of chlorine molecule. (Atomic Number of Chlorine = 17)
(ii) What happens when chlorine reacts with methane in the presence of sunlight ? Write the name of the reaction.
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(iii) Name the two oxidising agents used for the conversion of alcohols to acids. (iv) List four differences in properties between covalent compounds and ionic compounds.
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(b) (i) Give reason why carbon forms compounds mainly by covalent bonding. (ii) Why do covalent compounds have low melting and boiling points. (iii) Give reason for the following: I. Covalent compounds are bad conductors of electricity. II. Carbon shows catenation.
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A mild non-corrosive basic salt 'A', used for faster cooking, is strongly heated to produce a compound 'B', that is used for removing permanent hardness of water. Identify A and B and also write the equation for the reaction that occurs when A is heated.
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Explain giving reasons what happens to the rate at which the green plants will prepare food (I) during cloudy weather, and (II) when stomata get blocked due to dust.
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