CBSE Important Questions

Name one main ore of aluminium.

Why carbon tetrachloride (CC1₄) does not conduct electricity?

Which group of elements was missing in Mendeleev's Periodic Table?

State one point of similarity between the human eye and the camera.

The path of a beam of light passing through a true solution is not visible. Why?

The elements A, B and C are present in the same period of Periodic Table. Their atomic radii are 172 pm; 106 pm and 136 pm, respectively. Arrange these elements in increasing order of their atomic number in the period.

What type of bond is present in water molecule? Explain the formation of bonds between hydrogen and Oxygen to form water molecule.

How many electrons are associated with (i) one coulomb of charge? (ii) The flow of current of 16 mA for 100 s? (Given: charge of electron = 1.6 x 10¹⁹ C)

Two 'set-ups' are shown below: What are we likely to observe if the (i) Magnet in set-up (A) is kept stationary within the coil? (if) Key in set-up (B) is just 'plugged-in’?

Draw the pattern of the field lines of the magnetic field produced by a current carrying

1. Straight wire
2. circular coil
3. solenoid

How many 440 Q resistors should be connected in parallel to draw a total current of 10 A on a 220 V line?

Discuss the reaction of sodium, magnesium, iron and gold with water.

1. Give an example of the reaction between a non-metal oxide and sodium hydroxide. Write the balanced chemical equation also.
2. The pH of a solution is 4.8. What is its nature and what will be its action on blue litmus

The image, formed by a concave mirror, is observed to be

1. virtual, erect and larger than the object.
2. Real, inverted and larger than the object.
3. Real, inverted and of the same size as the object.
4. Real, inverted and smaller than the object.
   Where is the position of the object in each of these cases? Draw ray-diagrams to justify your choices
   for cases (I) and (III).

A beam of white light is made to fall on the three set-ups shown here.What are we likely to observe in each of these three cases ? How can we understand the similarity in the observations of cases(I) and (III)?
Name the seven colours linked with the observation in case (II) for sunlight

1. Write a reaction in which a gas is evolved.
2. What are oxidation-reduction reactions? Write the reaction of copper oxide with hydrogen and
   identify the species which is reduced.
3. What is rancidity?

How are chemical reactions classified? Describe the various types of reactions with the help of an
example in each case.