Q46 of 270 Page 68

On adding dilute hydrochloric acid to copper oxide powder, the solution formed is blue-green.

(a) Predict the new compound formed which imparts a blue-green colour to solution.


(b) Write a balanced chemical equation of the reaction which takes place.


(c) On the basis of the above reaction, what can you say about the nature of copper oxide?

(a) The new compound formed is cuprous chloride. It imparts a blue-green colour to the solution.

(b) CuO (s) + 2HCl (aq) → CuCl2 (aq) + H2O


(c) On observing the above reaction, it can be inferred that copper oxide is basic in nature. when limestone reacts with dilute HCl



More from this chapter

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44 When a piece of limestone reacts with dilute HO, a gas X is produced. When gas X is passed through water then a white precipitate Y is formed. On passing excess of gas X, the white precipitate dissolve forming a soluble compound Z.

(a) What are X, Y and Z?


(b) Write equations for the reactions which take place:


(i) when limestone reacts with dilute HCl


(ii) when gas X reacts with lime water to form white precipitate Y


(iii) when excess of gas X dissolves white precipitate Y to form a soluble compound Z

 45 If someone is suffering from the problem of acidity after overeating, which of the following would y suggest as remedy?

Lemon juice, Vinegar, Baking soda solution


Give reason for your choice.

 47 A white shirt has a yellow stain of curry. When soap is rubbed on this shirt during washing, the yellow stain turns reddish-brown. On rinsing the shirt with plenty of water, the reddish- brown stain turns yellow again.

(a) Name the natural indicator present in curry stain.


(b) Explain the changes in colour of this indicator which take place during washing and rinsing the shirt.


(c) What is the nature of soap (acidic/basic) as shown by the indicator present in curry stain?

 48 You have been provided with three test-tubes. One of these test-tubes contains distilled water and the other two contain an acidic and a basic solution respectively. If you are given only blue litmus paper, how will you identify the contents of each test- tube?