Board Paper of Class 10 2007 Science (SET 1) - Solutions

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

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

Approximately how many stars are there in the Milky Way?

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

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

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

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

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

(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.

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

Give reasons for the following:

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

(ii) Propanone forms addition product with HCN.

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

 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.

(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’.

(a) State Ohm’s Law.

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

(a) Name the chief ore of iron. Write its formula.

(b) How is an iron ore concentrated? Describe it briefly.

(c) Draw a labelled diagram of the blast furnace used in the extraction of iron from its concentrated ore.

OR

(a) Draw a labelled diagram of ‘Frasch process’ used for extracting sulphur.

(b) State the principle involved in the extraction of sulphur directly out of the ground.

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 labelled ray diagrams, show how this defect can be corrected.

(c) Name the type of lens used to correct this defect.

OR

(a) What is an electromagnet?
(b) List any of its two uses.
(c) Draw a labelled diagram to show how an electromagnet is made.
(d) What is the purpose of the soft iron core used in making an electromagnet?