1) The temperature of an open room of volume 30 m3 increases from 17° C to 27° C due to the sunshine . The atmosphere pressure in the room remains 1× 105 Pa. If ni and nf are the number of molecules in the room before and after heating , then nf -ni will be A) 1.38×1023 B) 2.5×1025 C) −2.5×1025 D) −1.61×1023 Answer: Option CExplanation:From pV=nRT=NNART We have, nf−ni=pVNARTf−pVNARTi ⇒nf−ni=105×308.30×6.02×1023 (1300−1290) =−2.5×1025 ∴ △n=−2.5×1025
