Gyan Bharti Online Test For Class 10th

1. Identify the substances that are oxidised and the substances that are reduced in the following reactions.

4Na (s) + O2 (g) → 2Na2O (s)

CuO (s) + H2 (g) → Cu (s) + H2O (l)

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2. Write the balanced equation for the following chemical reactions.

Hydrogen + Chlorine → Hydrogen Chloride

Barium Chloride + Aluminium Sulphate → Barium Sulphate + Aluminum Chloride

Sodium + Water → Sodium hydroxide + Hydrogen

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3. Which of the statements about the reaction below are incorrect? 2PbO (s) + C (s) → 2Pb (s) + CO2 (g) (a) Lead is getting reduced. (b) Carbon dioxide is getting oxidised. (c) Carbon is getting oxidised. (d) Lead oxide is getting reduced.

(a) and (b)

(a) and (c)

(a) , (b) and (c)

All

In the given reaction, lead oxide (PbO) is being reduced to lead (Pb), which means that lead is gaining electrons and its oxidation state is decreasing. Therefore, statement (a) is incorrect. On the other hand, carbon (C) is being oxidized to carbon dioxide (CO2), which means that carbon is losing electrons and its oxidation state is increasing. Therefore, statement (b) is also incorrect.

Explanation

In the given reaction, lead oxide (PbO) is being reduced to lead (Pb), which means that lead is gaining electrons and its oxidation state is decreasing. Therefore, statement (a) is incorrect. On the other hand, carbon (C) is being oxidized to carbon dioxide (CO2), which means that carbon is losing electrons and its oxidation state is increasing. Therefore, statement (b) is also incorrect.

4. Name the substance which on treatment with chlorine yields bleaching powder?

Calcium oxide

Calcium hydroxide [Ca(OH)2]

Calcium carbonate

Calcium sulphate

Calcium hydroxide is the substance that, when treated with chlorine, yields bleaching powder. Bleaching powder is a mixture of calcium hypochlorite (Ca(ClO)2) and calcium chloride (CaCl2), which are formed when chlorine gas reacts with calcium hydroxide. The reaction between chlorine and calcium hydroxide produces calcium hypochlorite, which is the active ingredient in bleaching powder and is responsible for its bleaching and disinfecting properties.

Explanation

Calcium hydroxide is the substance that, when treated with chlorine, yields bleaching powder. Bleaching powder is a mixture of calcium hypochlorite (Ca(ClO)2) and calcium chloride (CaCl2), which are formed when chlorine gas reacts with calcium hydroxide. The reaction between chlorine and calcium hydroxide produces calcium hypochlorite, which is the active ingredient in bleaching powder and is responsible for its bleaching and disinfecting properties.

5. What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer.

Hydrogen gas and iron chloride are produced.

Chlorine gas and iron hydroxide are produced.

No reaction takes place.

Iron salt and water are produced.

When dilute hydrochloric acid is added to iron filings, a chemical reaction occurs. The hydrogen ions from the hydrochloric acid react with the iron to form hydrogen gas, while the chloride ions combine with the iron to form iron chloride. Therefore, the correct answer is that hydrogen gas and iron chloride are produced.

Explanation

When dilute hydrochloric acid is added to iron filings, a chemical reaction occurs. The hydrogen ions from the hydrochloric acid react with the iron to form hydrogen gas, while the chloride ions combine with the iron to form iron chloride. Therefore, the correct answer is that hydrogen gas and iron chloride are produced.

6. What is the common name of the compound CaOCl2?

Washing soda

Baking soda

Plaster of paris

Bleaching powder

CaOCl2 is commonly known as bleaching powder. It is a white powder that is used for various purposes, including bleaching fabrics and disinfecting water. The compound is a mixture of calcium hypochlorite (Ca(ClO)2) and calcium chloride (CaCl2), which gives it its bleaching properties.

Explanation

CaOCl2 is commonly known as bleaching powder. It is a white powder that is used for various purposes, including bleaching fabrics and disinfecting water. The compound is a mixture of calcium hypochlorite (Ca(ClO)2) and calcium chloride (CaCl2), which gives it its bleaching properties.

7. Name the sodium compound which is used for softening hard water.

Baking soda

Baking powder

Washing soda

Gypsum

Washing soda, also known as sodium carbonate, is used for softening hard water. It is a common household product that can be added to laundry to help remove stains and soften water. Washing soda works by reacting with the minerals in hard water, such as calcium and magnesium, to form insoluble compounds that can be easily rinsed away. This helps to prevent the build-up of mineral deposits on clothes and in washing machines, resulting in cleaner and softer laundry.

Explanation

Washing soda, also known as sodium carbonate, is used for softening hard water. It is a common household product that can be added to laundry to help remove stains and soften water. Washing soda works by reacting with the minerals in hard water, such as calcium and magnesium, to form insoluble compounds that can be easily rinsed away. This helps to prevent the build-up of mineral deposits on clothes and in washing machines, resulting in cleaner and softer laundry.

8. A shiny brown-coloured element 'X' on heating in air becomes black in colour. Name the element 'X' _____ and the black coloured compound formed _____

When the shiny brown-colored element "X" is heated in air, it undergoes a chemical reaction and forms a black-colored compound. This indicates that the element "X" is copper (Cu) and the black-colored compound formed is copper oxide (CuO).

Explanation

When the shiny brown-colored element "X" is heated in air, it undergoes a chemical reaction and forms a black-colored compound. This indicates that the element "X" is copper (Cu) and the black-colored compound formed is copper oxide (CuO).

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