Option “C” is correct Pairs is correctly matched as such- Silver Iodide – Artificial rain, Silver Chloride – Horn Silver, Zinc Phosphide – Rat poison, Zinc Oxide – Philosopher’s wool.
202. In atom, neutron was discovered by:
1. J.J. Thomson
2. Chadwick
3. Rutherford
4. Newton
Option “B” is correct Neutron is a neutral particle which has no electrical charge. It was discovered by Chadwick in 1932.
203. The gas used to inflate the tyres of an aircraft is-
1. Hydrogen
2. Nitrogen
3. Helium
4. Neon
Option “B” is correct Nitrogen gas is used in the tyres of an aeroplane. This is because the nitrogen gas does not support combustion and can assist in preventing wheel fire when the aircraft lands .
204. Which of these consists carbon?
1. Lignite
2. Tin
3. Silver
4. Iron
Option “A” is correct Coal minerals are divided mainly into four types on the basis of the percentage of Carbon amount- Peat, Lignite, Bituminous and Anthracite.
205. Of how many carats is the pure gold?
1. 22
2. 24
3. 28
4. 20
Option “B” is correct It is an extension of the older carat (Karat in North American spelling) system of denoting the purity of gold by fractions of 24, such as ’18 carat’ for an alloy with 75% (18 parts per 24) pure gold by mass.
206. Radioactivity was discovered by:
1. Rutherford
2. Becquerel
3. Bohr
4. Benjamin Franklin
Option “B” is correct Radioactivity was discovered in 1896 by the French Scientist Henri Becquerel when he was working with phosphorescent materials.
207. Alkali metals can –
1. Be highly unstable at room temperature
2. Vaporize at room temperature
3. Easily gain electrons
4. Easily lose electrons
Option “D” is correct Alkali metals have one electron in their outer shell so alkali metal can easily lose electrons.
208. Why does Carbon Tetrachloride have no dipole moment?
1. Because of same size of carbon and chlorine atoms
2. Because of regular tetrahedral structure
3. Because of planar structure
4. Because of similar electron affinities of carbon and chlorine
Option “B” is correct Carbon Tetrachloride have no dipole moment because of regular tetrahedral structure.
Option “D” is correct Bupropion is used to treat major depressive disorder and to help people stop smoking.
210. Which of the following gases is heavier than oxygen?
1. Carbon dioxide
2. Ammonia
3. Methane
4. Helium
Option “A” is correct For oxygen, a molecule consists of two oxygen atoms, and has a weight of 2 x 16 = 32. For carbon dioxide, there is one carbon atom (weight 12) and two oxygen atoms (mass 16 x 2) for a total of 44. This means that carbon dioxide should be about 44/32 = 1.375 times (ideally) as heavy as an equivalent volume of oxygen. In reality, carbon dioxide is 1.383 times as heavy as oxygen.Even after solidification carbon di oxide is slightly heavier than similar volume of solid oxygen.
