161. The atomic number of chlorine is _______.
Answer: 17
162. In graphite, each carbon atom bonds with other carbon atoms in the same plane, forming a hexagonal arrangement.
Answer: Three
163. Generally, _______ have a sweet fragrance.
Answer: Esters
164. Rock salt is mined like _______.
Answer: Coal
165. _______ is used to remove the permanent hardness of water.
Answer: Washing soda
166. When a magnesium ribbon is burned in oxygen, it is converted into _______.
Answer: Magnesium oxide
167. CO(g) + 2H₂(g) → CH₃OH(g); X is
Answer: 1 atm
168. After two to three days of plastering, _______ forms and makes the walls shine.
Answer: Calcium carbonate
169. The decomposition of vegetable matter in compost is an example of _______ reaction.
Answer: Exothermic
170. When ferrous sulfate crystals [FeSO₄, 7H₂O] are heated, they release _______ and the color of the crystals changes.
Answer: Water
171. Sodium carbonate is obtained by heating _______.
Answer: Soda ash
172. The least good conductors of heat are _______.
Answer: Lead and mercury
173. Metals like potassium and sodium react rapidly with _______.
Answer: Cold water
174. If a metal is mercury, then the alloy is called _______.
Answer: Quicksilver amalgam
175. In the earth’s crust, only _______ carbon exists, and that too in the form of salts.
Answer: 0.002%
176. The atmosphere of Venus is composed of thick white and yellow clouds of _______.
Answer: Sulfuric acid
177. The major acid in blood is often used as an antacid.
Answer: Magnesium hydroxide
178. Dental enamel is the hardest substance in the body, made of ________.
Answer: Calcium hydroxyapatite
179. A bee sting injects an acid that causes pain and discomfort. The application of a mild alkali like _______ to the sting site provides relief.
Answer: Milk of magnesia
180. The aqueous solution of sodium chloride is called _______.
Answer: Brine