Bio gas production is more useful when compared to the direct use of dung because

• both fuel value and fertiliser value are effectively utilised

• production of bio gas involves less labour

• fuel is quickly produced

• the fertiliser produced is a fluid

42.

In blast furnace, iron oxide is reduced by

• hot blast of air

• carbon monoxide

• carbon

• silica

Use of chlorofluoro carbons is not encouraged because

• they are harmful to the eyes of people that use it

• they damage the refrigerators and air conditioners

• they eat away the ozone in the atmosphere

• they destroy the oxygen layer

Conversion of oxygen into ozone is non-spontaneous at

• all temperature

• high temperature

• room temperature

• low temperature

Which one of the following is not a common component of photo-chemical smog?

• Ozone

• Acrolein

• Peroxy acetyl nitrate

• Chloroflourocarbons

Producer gas is a mixture of:

• CO and N₂

• CO₂ and H₂

• N₂ and O₂

• CH₄ and N₂

The radiant energy from the sun is due to :

• combustion

• nuclear fusion

• nuclear fission

• chemical reaction

The smog is essentially caused by the presence of

• O₂ and O₃

• O₂ and N₂

• oxides of sulphur and nitrogen

• O₃ and N₂

Which of the following is responsible for depletion of the ozone layer in the upper strata of the atmosphere ?

• Polyhalogens

• Ferrocenes

• Fullerenes

• Freons

Match the Column I and Column II and choose the correct code given below.

Column I	Column II
A. Peroxyacetyl nitrile	i. Waste incineration
B. Indigo	ii. Vat dye
C. IR active molecules	iii. Global warming
D. Dioxins	iv. Photchemical smog

• A - iv; B - ii; C - iii; D - i

• A - i; B - ii; C - iv; D - iii

• A - ii; B - i; C - iv; D - iii

• A - iv; B - i; C - iii; D - ii