CBSE Class 10 Science Question Paper 2019 Set 04 Solved

CBSE Class 10 Science Question Paper Solved 2019 Set D. Students can download the last year board exams question papers using the link below. Free download of examination question papers with solutions. Last 10 year question papers should be practised to get better marks in examinations.

SECTION A

1. Name two industries based on forest produce.

2. Why are the heating elements of electric toasters and electric irons made of an alloy rather than a pure metal ?

SECTION B

3. Write the molecular formula of ethene and draw its electron dot structure.

4. Give reasons :

(a) Platinum, gold and silver are used to make jewellery.

(b) Metals like sodium and potassium are stored under oil.

OR

Silver articles become black when kept in open for some time, whereas copper vessels lose their shiny brown surfaces and gain a green coat when kept in open. Name the substances present in air with which these metals react and write the name of the products formed.

5. The absolute refractive index of Ruby is 1·7. Find the speed of light in Ruby. The speed of light in vacuum is 3 ×10⁸ m/s.

SECTION C

6. On heating blue coloured powder of copper (II) nitrate in a boiling tube, black copper oxide, O₂ and a brown gas X is formed.

(a) Identify the type of reaction and the gas X.

(b) Write balanced chemical equation of the reaction.

(c) Write the pH range of aqueous solution of the gas X.

7. (a) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid ?

(b) Dry hydrogen chloride gas does not change the colour of dry litmus paper. Why ?

OR

How is sodium hydroxide manufactured in industries ? Name the process. In this process a gas X is formed as by-product. This gas reacts with lime water to give a compound Y, which is used as a bleaching agent in the chemical industry. Identify X and Y and write the chemical equation of the reactions involved.

8. What are amphoteric oxides ? Give an example. Write balanced chemical equations to justify your answer.

9. What is a homologous series of carbon compounds ? Give an example and list its three characteristics. 

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