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In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

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Ques 14: In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved. Ans:   «« Previous question              Next question »»

What is the difference between displacement and double displacement reactions? Write equations for these reactions.

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Ques 13 : What is the difference between displacement and double displacement reactions? Write equations for these reactions.     Ans 13 : In a displacement reaction, a more reactive element replaces a less reactive element from a compound.                  A + BX → AX + B,      where A is more reactive than B In a double displacement reaction, two atoms or a group of atoms switch places to form new compounds.                   AB + CD → A D + BC For example: Displacement reaction: Double displacement reaction: «« Previous question              Next question »»

Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

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Ques 12: Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity. Ans 12:  (a) Thermal decomposition: (b) Decomposition by light: (c) Decomposition by electricity: «« Previous question              Next question »»

Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

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Ques 11: Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions. Ans 11: Decomposition reactions are those in which a complex compound breaks down to form two or  more substances. These reactions require a source of energy such as heat, light, etc. to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to   give a new substance with the release of energy. «« Previous question              Next question »»

Why is respiration considered an exothermic reaction? Explain.

Ques 10: Why is respiration considered an exothermic reaction? Explain. Ans 10: Energy is required to support our life. Energy in our body is obtained from the food we eat.   During digestion, large molecules of food/meals are broken down into simpler substances such as glucose. Glucose combines with oxygen( O 2)  in the cells and provides energy. The special name of this type of combustion reaction is respiration. Since energy is released in the whole process, it is an exothermic process.        C 6 H 12 O 6  + 6  O 2    → 6  CO 2  + 6  H 2 O «« Previous question              Next question »»

What does one mean by exothermic and endothermic reactions? Give examples.

Ques 9: What does one mean by exothermic and endothermic reactions? Give examples.   Ans 9: Chemical reactions that release energy in the form of heat, light, or sound are called  exothermic reactions. Example: Mixture of sodium and chlorine to yield table salt.                2 Na + Cl 2  →2 Na Cl In other words, combination reactions are exothermic.  Reactions that require energy or absorb   energy in order to proceed are called endothermic reactions.  For example: In the process of photosynthesis, plants use the energy from the sun to convert carbon dioxide and water to glucose and oxygen .       6  CO 2  + 6  H 2 O  →  C 6 H 12 O 6  + 6  O 2 «« Previous question              Next question »»

Write the balanced chemical equation for the following and identify the type of reaction in each case. (a)Potassium bromide + Barium iodide → Potassium iodide + Barium bromide(s)

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Ques 8: Write the balanced chemical equation for the following and identify the type of reaction in each case.  (a)Potassium bromide + Barium iodide → Potassium iodide + Barium bromide(s)   (b) Zinc carbonate→ Zinc oxide + Carbon dioxide  (c) Hydrogen + Chlorine→ Hydrogen chloride (d) Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen Ans 8:  «« Previous question              Next question »»

Write the balanced chemical equations for the following reactions. (a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water (b) Zinc + Silver nitrate → Zinc nitrate + Silver (c) Aluminium + Copper chloride → Aluminium chloride + Copper

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Ques 7: Write the balanced chemical equations for the following reactions.  (a) Calcium hydroxide Ca(OH) 2  + Carbon dioxide ( CO 2)   →Calcium carbonate (Ca  CO 3)  + Water( H 2 O)  (b) Zinc (Zn) + Silver nitrate (Ag N O 3)  → Zinc nitrate (Zn (N O 3 ) 2)   + Silver (Ag)  (c) Aluminium (Al) + Copper chloride (Cu  Cl 2)  → Aluminium chloride ( Al Cl 3)  + Copper (d) Barium chloride ( Ba Cl 2)  + Potassium sulphate → Barium sulphate + Potassium chloride Ans 7:  «« Previous question              Next question »»

Ques 6: Balance the following chemical equations.

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Ques 6: Balance the following chemical equations. Ans 6:  «« Previous question              Next question »»

Translate the following statements into chemical equations and then balance them. (a) Hydrogen gas combines with nitrogen to form ammonia. (b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide .

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Ques 5: Translate the following statements into chemical equations and then balance them.   (a) Hydrogen(H) gas combines with nitrogen(N) to form ammonia. (b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide(SO2) . (c) Barium chloride(Ba Cl2) reacts with aluminium sulphate to give aluminium chloride and a precipitate↓ of barium sulphate. (d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. Ans:  «« Previous question              Next question »»

What is a balanced chemical equation? Why should chemical equations be balanced?

Ques 4. What is a balanced chemical equation? Why should chemical equations be balanced? Ans 4: A reaction which has an equal number of atoms of all the elements on both sides of the  chemical equation is called a balanced chemical equation. The law of conservation of mass states that mass can neither be created nor destroyed. Hence, in a chemical reaction, the total mass of reactants should be equal to the total mass of the products. It means that the total number of atoms of each element should be equal on both sides of a chemical equation. Hence, it is for this reason that chemical equations should be  balanced. «« Previous question              Next question »»

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

Ques 3: What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer. (a) Hydrogen gas( H 2)  and iron chloride are produced.   (b) Chlorine gas( Cl 2)  and iron hydroxide are produced. (c) No reaction takes place. (d) Iron salt and water are produced. Ans 3: (a) Hydrogen gas( H 2)   and iron chloride are produced. The reaction is as follows:          Fe + 2 H Cl → Fe  Cl 2  + H2↑ «« Previous question               Next question »»

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