Question

Case study based questions

Passage 1

A cleaned magnesium ribbon about 3-4 cm long is burnt using a burner by

holding it with a pair of tongs and the ash so formed is collected in a

watch-glass. The magnesium ribbon is kept away as far as possible from

eyes.

1) What is the colour of the powder collected in a watch glass ?

a) White

b) Grey

c) Black

d) Brown.

2)Which type of change occurs in the above experiment ?

a) Physical

b) Chemical

c) No change.

3)What is the chemical name of the powder collected in a watch glass ?

a) Magnesium sulphide

b) Magnesium peroxide

c) Magnesium oxide

d) None of the above

4)Which of the following determines the occurrence of chemical reaction?

a) Change in state

b) Change in colour

c) Change in temperature

D) All the above.​

Answer 1

Explanation:

1 a

2 b

3 c

4 d

I hope my is right

Answer 2

The correct option to the following question is -

1. White - When the magnesium strip is burned by a burner, Magnesium oxide is formed. It is odourless and white in colour. So, the correct option is (a).
2. Chemical - chemical change occurs in the above experiment. Oxidation occurs, which is the addition of oxygen to the element. Oxidation is a chemical process. So, the correct option is (b).
3. Magnesium oxide - when magnesium is burnt, it will react with the oxygen, and so magnesium oxide is formed. So, the correct  option is (c)
4. All the above - Chemical reaction is determined by the change in state, change in colour, and change in temperature. So, the correct option is (d). It is a process that involves rearrangement of the molecular structure of a substance, as distinct from a change in physical form or a nuclear reaction.