BOARDS Chemical Reaction and Equation

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Que : MnO₂ + xHCl → MnCl₂ + yH₂O + zCl₂

In order to balance the above chemical equation, the values of x, y and z respectively are:

(a) 6, 2, 2               (b) 4, 1, 2                  (1Marks)

(c) 4, 2, 1                 (d) 2, 2, 1                    (2023) 

Ans:  

Que: Calcium oxide reacts vigorously with water to produce slaked lime.

CaO (s) + H₂O → Ca(OH)₂ (aq)

This reaction can be classified as:

(A) Combination reaction     
(B) Exothermic reaction
(C) Endothermic reaction                 (1 Marks)
(D) Oxidation reaction                         (2020)

Which of the following is a correct option?

(i) (A) and (C)                     (ii) (C) and (D)  

(iii) (A), (C) and (D)           (iv) (A) and (B)    

Ans:

Que: 2 g of ferrous sulphate crystals are heated in a dry boiling tube.             (3 Marks), (2019)

(a) List any two observations.

(b) Name the type of chemical reaction taking place.

(c) Write balanced chemical equation for the reaction and name the products formed.

Ans:

Que: The emission of Brown fumes in the given experimental setup is due to:
(a) thermal decomposition of lead nitrate which produces brown fumes of nitrogen dioxide.

(b) thermal decomposition of lead nitrate which produces brown fumes of lead oxide.

(c) oxidation of lead nitrate forming lead oxide and nitrogen dioxide.                     (1Marks)

(d) oxidation of lead nitrate forming lead oxide and oxygen.                                        (2023)
 
Ans:

Que: Select endothermic reaction from the following:         

(a) Decomposition of vegetable matter into compost.

(b) Decomposition of calcium carbonate to form quick lime and carbon dioxide.

(c) Burning of a candle.                 (1Marks)

(d) Process of respiration.              (2023)

Ans:

Que: What would you observe on adding zinc granules to freshly prepared ferrous sulphate solution ? Give reason for your answer.                   (2 Marks), (2019)

Ans: 

Que : Assertion (A): The colour of aqueous solution of copper sulphate turns colourless when a piece of lead is added to it.

Reason (R) Lead is more reactive than copper, and hence displaces copper from its salt solution.

(a) Both (A) and (R) are true and (R) is the correct explanation of (A).

(b) Both (A) and (R) are true, but (R) is not the correct explanation of (A).

(c) (A) is true, but (R) is false.             (1Marks)

(d) (A) is false, but (R) is true.                (2023)

Ans:

Que: When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained, and the sulphuric acid so formed remains in the solution.

The reaction is an example of a:

(a) Combination reaction 
(b) Displacement reaction
(c) Decomposition reaction                (1Marks)
(d) Double displacement reaction      (2020)

Ans:

Que: Identify the type of reactions taking place in each of the following cases and write the balanced chemical equation for the reactions.

(a) Zinc reacts with silver nitrate to produce zinc nitrate and silver.          (3 Marks), (2019)

(b) Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead iodide.

Ans:

Que: (a) Identify the reducing agent in the following reactions:

(i) NH₃ + O₂  →  NO + H₂O

(ii) H₂O + F₂ → HF + HOF

(iii) Fe₂O₃ + CO → Fe + CO₂                (3 Marks)

(iv) H₂ + O₂ → H₂O                                 (2023)

(b) Define a redox reaction in terms of gain or loss of oxygen.  

Que: 1g 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 reactions, The name and the color of the products formed in each case.                            (3 Marks), (2020)

Ans:

Que: 2 g of silver chloride is taken in a china dish and the china dish is placed in sunlight for sometime. What will be your observation in this case? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction. (3 Marks), (2019)

Ans:

Que: You might have noted that when copper powder is heated in a china dish, the reddish brown surface of copper powder becomes coated with a black substance. (3 Marks), (2019)

(a) Why has this black substance formed?

(b) What is this black substance?

(c) Write the chemical equation of the reaction that takes place

(d) How can the black coating on the surface be turned reddish brown ?

Ans:

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