When 2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc in a test tube and then warmed, the reaction that occurs can be written in the form of a balanced chemical equation as:
a.
NaOH + Zn -> NaZnO + H2O
b.
2NaOH + Zn -> Na2ZnO2 + H2
Correct Answer
c.
2NaOH + Zn -> NaZnO + H2
d.
2NaOH + Zn -> Na2ZnO2 + H2O
Step-by-Step AI Explanation
Verified Method
When zinc reacts with sodium hydroxide, it forms sodium zincate (Na2ZnO2) and releases hydrogen gas. The balanced chemical equation is 2NaOH + Zn -> Na2ZnO2 + H2. Option A, C, and D are incorrect due to wrong chemical formulas or incorrect stoichiometry.
Q2mcq1 mark
Select from the following a decomposition reaction in which the source of energy for decomposition is light:
a.
2FeSO4 -> Fe2O3 + SO2 + SO3
b.
2H2O -> 2H2 + O2
c.
2AgBr -> 2Ag + Br2
Correct Answer
d.
CaCO3 -> CaO + CO2
Step-by-Step AI Explanation
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The decomposition of silver bromide (AgBr) into silver (Ag) and bromine (Br2) is a photochemical decomposition reaction, meaning it requires light energy. Option A uses heat, Option B uses electricity, and Option D uses heat.
Q3mcq1 mark
A metal and a non-metal that exist in liquid state at the room temperature are respectively:
a.
Bromine and Mercury
b.
Mercury and Iodine
c.
Mercury and Bromine
Correct Answer
d.
Iodine and Mercury
Step-by-Step AI Explanation
Verified Method
Mercury (Hg) is the only metal that is liquid at room temperature, and Bromine (Br) is the only non-metal that is liquid at room temperature. The question asks for the metal first and the non-metal second, making (c) correct.
Q4mcq1 mark
Carbon compounds:
(i) are good conductors of electricity.
(ii) are bad conductors of electricity.
(iii) have strong forces of attraction between their molecules.
(iv) have weak forces of attraction between their molecules.
The correct statements are:
a.
(i) and (ii)
b.
(ii) and (iii)
c.
(ii) and (iv)
Correct Answer
d.
(i) and (iii)
Step-by-Step AI Explanation
Verified Method
Carbon compounds are generally covalent, meaning they do not have free electrons or ions, making them poor (bad) conductors of electricity (ii). Covalent compounds also typically have weak intermolecular forces of attraction (iv), which explains their low melting and boiling points.
Q5mcq1 mark
Consider the following compounds:
FeSO4, CuSO4, CaSO4, Na2CO3
The compound having the maximum number of water of crystallisation in its crystalline form in one molecule is:
a.
FeSO4
b.
CuSO4
c.
CaSO4
d.
Na2CO3
Correct Answer
Step-by-Step AI Explanation
Verified Method
The chemical formulas for these in crystalline form are: FeSO4·7H2O (7 molecules), CuSO4·5H2O (5 molecules), CaSO4·2H2O (2 molecules), and Na2CO3·10H2O (10 molecules). Na2CO3 has the highest number of water molecules (10).
Q6mcq1 mark
Oxides of aluminium and zinc are:
a.
acidic
b.
basic
c.
amphoteric
Correct Answer
d.
neutral
Step-by-Step AI Explanation
Verified Method
Amphoteric oxides are metal oxides that react with both acids and bases to produce salt and water. Aluminium oxide (Al2O3) and Zinc oxide (ZnO) are classic examples of amphoteric oxides.
Q7mcq1 mark
MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2
The reaction given above is a redox reaction because in this case:
a.
MnO2 is oxidised and HCl is reduced.
b.
HCl is oxidised.
c.
MnO2 is reduced.
d.
MnO2 is reduced and HCl is oxidised.
Correct Answer
Step-by-Step AI Explanation
Verified Method
In this reaction, MnO2 loses oxygen to become MnCl2 (reduction), and HCl loses hydrogen/gains oxygen (as part of Cl2) to be oxidised. Therefore, MnO2 is reduced and HCl is oxidised.
Q8mcq1 mark
Consider the following statements:
(i) The sex of a child is determined by what it inherits from the mother.
(ii) The sex of a child is determined by what it inherits from the father.
(iii) The probability of having a male child is more than that of a female child.
(iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote.
The correct statements are:
a.
(i) and (iii)
b.
(ii) and (iv)
Correct Answer
c.
(iii) and (iv)
d.
(i), (iii) and (iv)
Step-by-Step AI Explanation
Verified Method
The sex of a child depends on whether an X-carrying or Y-carrying sperm fertilizes the ovum. Since the father provides either an X or a Y chromosome, the father determines the sex (ii). This determination happens at fertilization (iv). Statement (i) is false because the mother only provides X, and (iii) is false as the ratio is equal (50:50).
Q9mcq1 mark
Chromosomes:
(i) carry hereditary information from parents to the next generation.
(ii) are thread-like structures located inside the nucleus of an animal cell.
(iii) always exist in pairs in human reproductive cells.
(iv) are involved in the process of cell division.
The correct statements are:
a.
(i) and (ii)
b.
(iii) and (iv)
c.
(i), (ii) and (iv)
Correct Answer
d.
(i) and (iv)
Step-by-Step AI Explanation
Verified Method
Statements (i), (ii), and (iv) are correct. Chromosomes carry genetic information (DNA), are located in the nucleus, and are crucial during cell division (mitosis/meiosis). Statement (iii) is incorrect because human reproductive cells (gametes) are haploid and contain only half the number of chromosomes (they do not exist in pairs).
Q10mcq1 mark
In a nerve cell, the site where the electrical impulse is converted into a chemical signal is known as:
a.
Axon
b.
Dendrites
c.
Neuromuscular junction
Correct Answer
d.
Cell body
Step-by-Step AI Explanation
Verified Method
The neuromuscular junction (or synapse) is the point of contact between a nerve terminal and another cell, where electrical impulses are converted into chemical signals via neurotransmitters. Dendrites and axons transmit the signal, and the cell body processes it, but the conversion specifically occurs at the junction.
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A stomata closes when:
(i) it needs carbon dioxide for photosynthesis.
(ii) it does not need carbon dioxide for photosynthesis.
(iii) water flows out of the guard cells.
(iv) water flows into the guard cells.
The correct reason(s) in this process is/are:
a.
(i) only
b.
(i) and (ii)
c.
(ii) and (iii)
d.
(ii) and (iv)
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Assertion (A): Hydrogen gas is not evolved when zinc reacts with nitric acid. Reason (R): Nitric acid oxidises the hydrogen gas produced to water and itself gets reduced.
a.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
b.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the 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): Accumulation of harmful chemicals is maximum in the organisms at the highest trophic level of a food chain. Reason (R): Harmful chemicals are sprayed on the crops to protect them from diseases and pests.
a.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
b.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the 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): The rate of breathing in aquatic organisms is much faster than in terrestrial organisms. Reason (R): The amount of oxygen dissolved in water is very high as compared to the amount of oxygen in air.
a.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
b.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the 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): The rainbow is a natural spectrum of sunlight in the sky. Reason (R): The rainbow is formed in the sky when the sun is overhead and water droplets are also present in the air.
a.
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
b.
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the 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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Name the type of chemical reaction in which calcium oxide reacts with water. Justify your answer by giving balanced chemical equation for the chemical reaction.
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(A) How is the movement of leaves of a sensitive plant different from the downward movement of the roots? OR (B) There is a hormone which regulates carbohydrate, protein, and fat metabolism in our body. Name the hormone and the gland which secretes it. Why is it important for us to have iodised salt in our diet?
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(B) There is a hormone which regulates carbohydrate, protein, and fat metabolism in our body. Name the hormone and the gland which secretes it. Why is it important for us to have iodised salt in our diet?
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Write one chemical equation each for the chemical reaction in which the following have taken place: (i) Change in colour (ii) Change in temperature (iii) Formation of precipitate
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(i) The pH of a sample of tomato juice is 4.6. How is this juice likely to be in taste? Give reason to justify your answer. (ii) How do we differentiate between a strong acid and a weak base in terms of ion-formation in aqueous solutions? (iii) The acid rain can make the survival of aquatic animals difficult. How?
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(i) Why is respiratory pigment needed in multicellular organisms with large body size? (ii) Give reasons for the following: (a) Rings of cartilage are present in the throat. (b) Lungs always contain a residual volume of air. (c) The diaphragm flattens and ribs are lifted up when we breathe in. (d) Walls of alveoli contain an extensive network of blood vessels.
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(i) Why is respiratory pigment needed in multicellular organisms with large body size? (ii) Give reasons for the following: (a) Rings of cartilage are present in the throat.
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Study the diagram given below and answer the questions that follow: (i) Name the defect of vision represented in the diagram. Give reason for your answer. (ii) List two causes of this defect. (iii) With the help of a diagram show how this defect of vision is corrected.
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Name and state the rule to determine the direction of a: (i) Magnetic field produced around a current carrying straight conductor. (ii) Force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it.
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(A) Plants → Deer → Lion. In the given food chain, what will be the impact of removing all the organisms of the second trophic level on the first and third trophic level? Will the impact be the same for the organisms of the third trophic level in the above food chain if they were present in a food web? Justify.
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(B) A gas 'X' which is a deadly poison is found at the higher levels of atmosphere and performs an essential function. Name the gas and write the function performed by this gas in the atmosphere. Which chemical is linked to the decrease in the level of this gas? What measures have been taken by an international organisation to check the depletion of the layer containing this gas?
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(A) (i) Define a homologous series of carbon compounds. (ii) Why is the melting and boiling points of CH26 higher than that of CH24 or CH22? (iii) Why do we NOT see any gradation in chemical properties of a homologous series compounds? (iv) Write the name and structures of (i) aldehyde and (ii) ketone with molecular form C3H6O.
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(B) (i) Write the name and structure of an organic compound 'X' having two carbon atoms in its molecule and its name is suffixed with '-ol'. (ii) What happens when 'X' is heated with excess concentrated sulphuric acid at 443 K? Write chemical equation for the reaction stating the conditions for the reaction. Also state the role played by concentrated sulphuric acid in the reaction. (iii) Name and draw the electron dot structure of hydrocarbon produced in the above reaction.
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(A) (i) Name three techniques/devices used by human females to avoid pregnancy. Mention the side effects caused by each. (ii) What will happen if in a human female (a) fertilisation takes place, (b) an egg is not fertilised?
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(B) (i) You have two beakers 'A' and 'B' containing copper sulphate solution. What would you observe after about 15 hours if you dip a strip of zinc in beaker 'A' and a strip of iron in beaker 'B'? Give reason for your observations in each case.
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(iii) (A) In a cross with two pairs of contrasting characters RRYy × rryy. Mendel observed 4 types of combinations in F2 generation. By which method did he obtain F2 generation? Write the ratio of the parental combinations obtained and what conclusions were drawn from this experiment.
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(i) When Mendel crossed pea plants with pure tall and pure short characteristics to produce F1 progeny, which two observations were made by him in F1 plants?
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Study the data given below showing the focal length of three concave mirrors A, B, and C and the respective distances of objects placed in front of the mirrors: Case 1: Mirror A, Focal Length 20cm, Object Distance 45cm; Case 2: Mirror B, Focal Length 15cm, Object Distance 30cm; Case 3: Mirror C, Focal Length 30cm, Object Distance 20cm. (i) In which one of the above cases the mirror will form a diminished image of the object? Justify your answer. (ii) List two properties of the image formed in case 2. (iii) (A) What is the nature and size of the image formed by mirror C? Draw a ray diagram to justify your answer.
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Draw a diagram showing spore formation in Rhizopus and label the (a) reproductive and (b) non-reproductive parts. Why does Rhizopus not multiply on a dry slice of bread?
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An electric oven is designed to work on the mains voltage of 220 V. This oven consumes 11 units of electrical energy in 5 hours. Calculate: (a) power rating of the oven (b) current drawn by the oven (c) resistance of the oven when it is red hot.
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Write the relation between resistance R and electrical resistivity ρ of the material of a conductor in the shape of a cylinder of length l and area of cross-section A. Hence derive the SI unit of electrical resistivity.
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The resistance of a metal wire of length 3 m is 60 Ω. If the area of cross-section of the wire is 7.2 * 10^-4 m^2, calculate the electrical resistivity of the wire.
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