CBSE - X

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CBSE X
SCIENCE AND TECHNOLOGY (Theory) 2007
(OUTSIDE DELHI)

Time allowed: 2 hours 15 mins; Maximum Marks: 100

General Instructions:
1) The question paper comprises of two sections A and B. You are to attempt both sections.
2) You are advised to attempt all the questions of Section A and Section B separately.
3) All questions are compulsory.
4) There is no overall choice. However, internal choice has been provided in some questions. You are to attempt only one option in such questions.
5) Marks allocated to every question are indicated against it.
6) Questions number 1-4 in Section A and 17, 18 in Section B are very short answer questions. These are to be answered in one word or one sentence.
7) Questions number 5-8 in Section A and 19, 20 in Section B are short answer questions. These are to be answered in 30 - 40 words each.
8) Questions number 9-14 in Section A and 21 - 23 in Section B are also short answer questions.These are to be answered in 40 - 50 words each.
9) Questions number 15, 16 in Section A and 24 in Section B are long answer questions. These are to be answered in 70 words each.
SECTION A

Question 1

1. What is the role of a catalyst in a chemical reaction?

Question 2

2. Which class of compounds gives a positive Fehling’s test ? 

Question 3

3. Approximately how many stars are there in the Milky Way ?

Question 4

4. What is meant by the statement, “Potential difference between points A and B in an electric field is 1 volt.”?

Question 5

5. State the ‘Law of Chemical Equilibrium’. Write an expression for the equilibrium constant (K) for the reaction,

Question 6

6. Name the organic acid present in vinegar. Write a chemical equation which represents the commercial method for the preparation of this acid from ethanol.

Question 7

7. Distinguish between ‘artificial’ and ‘natural’ satellites. Why artificial satellites are called “eyes in the sky” ? 

Question 8

8. An electric lamp is marked 100 W, 220 V. It is used for 5 hours daily. Calculate

(i) its resistance while glowing.

(ii) energy consumed in kWh per day.

Question 9

9. (a) Write the chemical name and formula of bleaching powder.
(b) Why does bleaching powder smell of chlorine when exposed to air?
(c) Write chemical equation to represent the action of dilute hydrochloric acid on bleaching powder.

Question 10

10. What is meant by ‘dehydrating agent’? Describe with a chemical equation, an activity to show that concentrated sulphuric acid is a strong dehydrating agent.

Question 11

11. Give reasons for the following :

(i) Oxidation of ethanol with CrO3 produces ethanal while ethanol when oxidised with alkaline KMnO4 produces ethanoic acid. (out of syllabus)

(ii) Propanone forms addition product with HCN.(out of syllabus)

(iii) Alcohol supplied for industrial purposes is mixed with copper sulphate.


Question 12

12. An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.

Question 13

13. (a) State one limitation of solar energy available from solar cells.

(b) What is the minimum wind velocity required to obtain useful energy with a windmill?

(c) Define the term ‘nuclear fission’.

Question 14

14.(a) State Ohm’s Law.
(b) Draw a schematic diagram of the circuit for studying Ohm’s Law.

Question 15

15(a) Name the chief ore of iron. Write its formula. (b)How is an iron ore concentrated? Describe it briefly. (out of syllabus)
(c)Draw a labeled diagram of the blast furnace used in the extraction of iron from its concentrated ore.

OR

(a) Draw a labeled diagram of ‘Frasch process’ used for extracting sulphur. (b) State the principle involved in the extraction of sulphur directly out of the    ground.

Question 16

16. A 14-year old student is not able to see clearly the questions written on the blackboard placed at a distance of 5 m from him.
(a) Name the defect of vision he is suffering from.
(b) With the help of labeled ray diagrams show how this defect can be corrected.
(c) Name the type of lens used to correct this defect.

                                                                Section B
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