CBSE Class 11 Chemistry VBQs Hydrogen

UNIT – 9 (HYDROGEN)

Question. Prakash was surprised to see that air painting get furnished. Prakash discussed this matter with his elder brother Manoj. He also wanted to Manoj explained him the reason and also the method to restore the original whiteness.

(a) Can you predict what explanation was given by Manoj?

(b) Analyse the attitude of both Prakash and Manoj?

(c) H₂O₂ act as an oxidizing agent as well as reducing agent. Why?

Question. Teacher told the students that water should that water should be softened before using in boilers. Karina one of the students, asked the reason. The teachers explained the reason in detail to him and then Karina got satisfied.

(a) Predict the explanation given by the teacher.

(b) Temporary hard water becomes soft on boiling. Why?

(c) What values are displayed by Karina.

Question. Hard water is unfit for its use in the laboratory and laundry because of the presence of chlorides of calcium and magnesium. One way to remove these ions from hard water is the use of sodium carbonate. Your teacher asked you to calculate the amount of sodium required to remove the calcium ions from a sample of hard water which is 0.002 M in calcium ions.

(a) Write the reaction of sodium carbonate in the removal of hardness of water.

(b) What mass of sodium Carbonate is required to remove the calcium ions from a sample of 1000 litres of hard water?

(c) Write the value associated with this problem.

Question. A compound of hydrogen and oxygen has empirical formula OH. This compound is used to restore the colour of old oil paintings containing lead oxide. This compound also liberates iodine from an acidified solution of potassium iodide.

(a) Name this compound and write its formula.

(b) Write a balanced chemical equation to show the restoration of colours of the old painting by this compound.

(c) Mention the value associated with the function of this compound.

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