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

The pH values of three solutions A, B, and C having equal molar concentration are respectively 2.0, 7.0, and 13.0 at 298 K. Which of the three solutions represents an acid solution?

Write the chemical formula of simplest ketone.

Why is our galaxy called ‘Milky Way’?

If the distance between two electric charges is doubled, how much will the force exerting between them changes to?

State four characteristic features of ‘Dynamic Equilibrium’.

What is Fehling’s reagent? What would you observe on heating formalin with Fehling’s reagent in a test tube?

Distinguish between a ‘geosynchronous’ and a ‘polar’ satellite. What is the usual time period of a

(a) geosynchronous satellite
(b) polar satellite

An electric heater is used on 220 V supply and takes a current of 3.4 A. Calculate (i) its power and (ii) its resistance, when it is in use.

What is ‘Plaster of Paris’ chemically? How is it obtained from gypsum? Write the condition and chemical equation involved in its manufacture.

Define the term, ‘allotropy’. In which kind of properties are the two allotropes of an element (i) similar, (ii) different? How can the two allotropes of sulphur be distinguished from one another?

Give reasons for the following:

(a) Alcohol supplied for industrial purposes is mixed with poisonous substances such as copper sulphate.

(b) The reaction is classified as a decarboxylation reaction.

(c) Formalin is used for preserving biological specimens.

A convex mirror used on a bus has a focal length of 200 cm. If a scooter is located at 400 cm from this mirror, find the position, nature and magnification of the image formed in the mirror.

(a) What is a ‘solar cell’?
(b) Why is biogas considered an ideal fuel for domestic use?
(c) Name a device in which controlled chain reaction is used.

(a) Define the term ‘electroplating’.

(b) With a labelled diagram describe an activity to show copper plating on a metal spoon.

(a) Write the name and formula of the main ore of aluminium.
(b) What is alumina? Which reducing agent is used for the reduction of alumina?
(c) Draw a diagram of the electrolytic cell used in the reduction of alumina. Label anode and cathode on it.
(d) Why is alumina dissolved in cryolite?

OR

(a) What is an alloy? How is an alloy made?
(b) Name an alloy
(i) which has a lower melting point than its constituents
(ii) which is more hard, tough and strong than its constituents
(c) Name the constituents of the alloy ‘Magnalium’. Write its two uses.

Name the four common defects of vision and state the cause of each defect. A person cannot see distinctly objects placed beyond 2 metres. State the nature and focal length of the lens which could be used to correct this defect.

OR

(a) Describe with diagram an experiment to show that a force is exerted on a current carrying conductor when placed perpendicular in a magnetic field.

(b) State the rule to find the direction of the force exerted on a current carrying conductor in a magnetic field.