161. The permanent hardness of water can be removed by adding —
Answer: Washing Soda

162. The alcohol used in power alcohol is
Answer: ethyl alcohol

163. The cell membrane is–
 Answer:  semipermeable

164. The chemical used as a fixer in photography is
Answer: sodium thiosulphate

165. Which of the following substance is a bad conductor of electricity but a good conductor of heat?
Answer: Mica

166. Polythene is industrially prepared by the polymerisation of–
Answer: ethylene

167. The shell of the egg is made of –
Calcium Carbonate.

168. Talc is basic –
magnesium silicate mineral

169. The highest and simplest element is hydrogen while the lightest metal is-
Lithium

170. Temporary hardness of water is due to the bicarbonates of calcium and magnesium. It can be removed by –
boiling or adding lime  

171. Sodium is stored in Kerosene to prevent-
oxidation.

172. Permanent hardness is due to the presence of sulphates and chlorides of calcium and magnesium. It can be removed by –
Adding washing soda or by distillation

173. NPK mixtures are fertilizers with the mixtures of –
nitrogen, phosphorous and potassium.

174. The gas responsible for the Bhopal Gas Tragedy is –
Methyl Isocyanate (MIC)

175. CO2 is used as-
 fire extinguishers.

176.Thorium is extracted from –
monozite sand.

177. Red phosphorus is used in :
Making matches

178. In a dry cell, zinc and carbon act as-
electrodes.

179. Chlorine is used as a-
 bleaching agent.

180. Lead pencils contain –
graphite.

181. White phosphorus is a –
strong poison.

182. Carborundum is used as an abrasive for-
 cutting and grinding glasses.

183. Silver iodide is used to make –
artificial rain.

184. Zinc oxide is called the-
 ‘flower of Zinc”

185. Water is called –
‘Universal Solvent”

186. The gas used in refrigerators is-
 ammonia.

187. The lightest substance known is Hydrogen and the heaviest is –
Osmium.

188. Con. Nitric acid is used to-
 purify gold.

189. A mixture of salt and ice gives a temperature below 0°c which is called Antifreeze. It is used to –
breakdown ice mixtures in the radiators of cars in cold countries.

 

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