281. Urea as a fertilizer contains:____________?
A. 57% N
B. 73% N
C. 46% N
D. 53% N

282. Which of the following is not the name of any scientist?
A. Pauli exclusion principle
B. Hund’s rule
C. Aufbau’s principle
D. Le-Chatelier’s principle

283. For the generation of biogas, the materials commonly used are__________?
A. Animal wastes
B. Forest residues
C. Aquatic plants
D. None of these

284. Give Electronic configuration of Sodium:
A. 1s2,2s2,2p6
B. 1s2,2s2,2p6,3s2
C. 1s2,2s2,2p6,3s1
D. None of these

285. Air is a/an _________?
A. Compound
B. Element
C. Electrolyte
D. Mixture

286. The element used for the formation of alloys is__________?
A. Iron
B. Calcium
C. Mercury
D. Chromium

287 The Bond Energy of H-F is________?
A. 456kJ/mol
B. 562kJ/mol
C. 281kJ/mol
D. None

288. One fathom is equal to:__________?
A. 6 feet
B. 6 meters
C. 60 feet
D. 100 cm

289. What are the metal bearing rocks called?
A. Bitumen
B. Bauxite
C. Metalloids
D. Ores

290. Soil pollution is caused by:_________?
A. Aerosol
B. Ozone
C. Acid rain
D. PAN