221. The gas evolved when manganese reacts with very dilute HNO₃ is _______.
Answer: NO₂
222. The order of reactivity is _______.
Answer: Al > Mg > Zn > Fe
223. Cinnabar is _______.
Answer: HgS
224. Sulfide ores are converted to oxides by _______.
Answer: Roasting
225. Fe₂O₃(s) + 2Al(s) → 2Fe(s) + Al₂O₃(s) + Heat. This reaction is known as _______.
Answer: Thermite Reaction
226. Silver items turn black after some time of exposure to air. This is due to a _______ coating.
Answer: Silver Sulfide
227. _______ is an alloy of.
Answer: Cu & Sn
228. _______ alloy is used for joining electrical wires.
Answer: Solder
229. The main component of CNG is _______.
Answer: Methane
230. _______ is used as a catalyst for the hydrogenation of vegetable oils.
Answer: Ni
231. Dehydration of ethanol gives _______.
Answer: Ethene
232. A solution of acetic acid in water _______ is called vinegar.
Answer: 6-9%
233. The melting point of pure ethanoic acid is _______.
Answer: 290 K
234. Ester reacts in the presence of acid or base to give alcohol and carboxylic acid. This is called _______.
Answer: Hydrolysis
235. The properties of elements are periodic functions of their _______.
Answer: Atomic Number
236. There are _______ periods in the modern periodic table.
Answer: 7
237. Metalloids (metal-like elements) are _______.
Answer: Silicon
238. There are _______ electrons in the M shell of chlorine.
Answer: 7
239. Metal oxide + acid → X + water, X is _______.
Answer: Salt
240. The hydronium ion is _______.
Answer: H₂O+