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The step(s) necessary for determining the percentage of water absorbed by raisins is/are:
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In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?
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Distinguish between ionic and covalent compounds under the following properties:
(i) Strength of forces between constituent elements
(ii) Solubility of compounds in water
(iii) Electrical conduction in substances
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Show the formation of Na2O by the transfer of electrons.
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Identify the type of reaction taking place of the following case and write the balanced chemical equation of the reaction:
Zinc reacts with silver nitrate to produce zinc nitrate and silver.
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Identify the type of reaction taking place of the following case and write the balanced chemical equation of the reaction:
Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead iodide.
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Answer the following question.
What is methane? Draw its electron dot structure. Name the type of bonds formed in this compound. Why are such compounds:
(i) poor conductors of electricity? and
(ii) have low melting and boiling points? What happens when this compound burns in oxygen?
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Answer the following question.
What is observed when 2 mL of dilute hydrochloric acid is added to 1 g of sodium carbonate taken in a clean and dry test tube? Write a chemical equation for the reaction involved.
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| Human body is made up of five important components, of which water is the main component. Food, as well as potable water, are essential for every human being. The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields. These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants. As these chemicals are not biodegradables, they get accumulated progressively at each trophic level. The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body. |
- Why is the maximum concentration of pesticides found in human beings? (1)
- Give one method which could be applied to reduce our intake of pesticides through food to some extent. (1)
- Various steps in a food chain represent: (1)
- Food web
- Trophic level
- Ecosystem
- Biomagnification
- With regard to various food chains operating in an ecosystem, man is a: (1)
- Consumer
- Producer
- Producer and consumer
- Producer and decomposer
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1 g of copper powder was taken in a China dish and heated. What change takes place on heating? When hydrogen gas is passed over this heated substance, a visible change is seen in it. Give the chemical equations of reactions, the name and the color of the products formed in each case.
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What is thermit process?
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Name the substance that is getting oxidised in the thermit process.
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Write the name and molecular formula of a carbon compound having its name suffixed with "-ol" and having two carbon atoms in its molecule. With the help of a chemical equation indicate what happens when this compound is heated with excess conc. H2SO4.
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When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.
What is the colour of this precipitate? Name the compound precipitated.
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When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.
Write the balanced chemical equation for this reaction.
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What are decomposers? What will be the consequence if the decomposers are completely eradicated from an ecosystem? Give justification in support of your answer.
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A student mixes sodium sulphate powder in barium chloride powder. What change would the student observe on mixing the two powders? Justify your answer and explain how he can obtain the desired change.
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List two differences between the properties exhibited by covalent compounds and ionic compounds.
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Which of the following is the purest form of carbon?
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Which of the following ray diagrams is correct for the ray of light incident on a lens shown in figure?
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| A | B |
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| C | D |
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