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Hydrogen

Short Answer Type

151.

Complete the following chemical reactions.
PbS + H₂O₂ (aq) $rightwards arrow$

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152.

Complete the following chemical reactions.
$MnO subscript 4 superscript minus left parenthesis aq right parenthesis space plus space straight H subscript 2 straight O subscript 2 left parenthesis aq right parenthesis space rightwards arrow$

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153.

How does hydrogen peroxide act as bleaching agent?

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154.

Give two chemical reactions which show the acidic character of hydrogen peroxide.

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155. Hydrogen peroxide is used to restore the colour of old oil paintings containing lead oxide. Write a balanced equation for the reaction that takes place in this process.

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Long Answer Type

156. What is the structure of hydrogen peroxide? Draw a schematic diagram indicating the shape of the molecule clearly.

The structure of hydrogen peroxide has been established by X-ray studies.

(i) The molecule of hydrogen peroxide is not planar. It is described as an ‘open book structure.

(ii) The O – O part of the molecule can be thought of as lying on the spine of a book open at an angle of 90°.

(iii) The hydrogen atoms are placed one on each cover.

(iv) The H – O bonds make an angle of about 101.5° with the O – O bond as shown.

(v) The O – O linkage present between two oxygen atoms is called peroxybond (peroxide linkage).

(vi) This O – O linkage results from a p-p overlap of the p-orbitals of the two oxygen atoms.

(vii) Each H – O bond results from an s-p overlap between s-orbital of hydrogen and p-orbital of the oxygen atom.

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