31.Acidified potassium dichromate is treated with hydrogen sulfide. In the reaction, the oxidation number of chromium A) Increases from + 3 to +6 B) Decreases from+6 to+3 C) Remains unchanged D) Decreases from +6 to +2 View Answer Report DiscussAnswer: Option BExplanation:Decreases from +6 to+3. K2Cr2O7+ 4H2SO4 → K2SO4 + Cr2 (SO4 )3 + 4H2O + 3O [H2S + [O]→ S+H2O]×3 +6 +3 K2Cr2O7+ 4H2SO4 + 3H2S → K2SO4 + Cr2 (SO4 )3 +7H2O+3S
32.Arrange the following particles in increasing order of values of e/m ratio : electron (e), proton (p), neutron (n) and $\alpha$-particle ($\alpha$) - A) n, p, e, $\alpha$ B) n, $\alpha$, p, e C) n, p, $\alpha$, e D) e, p, n, $\alpha$ View Answer Report DiscussAnswer: Option BExplanation: Electron Proton Neutron α-Particle e 1 Unit 1 Unit Zero 2 Units m 1/1837 Unit 1 Unit 1 Unit 4-Units e/m 1837 1 Zero 1/2
33.The work done in ergs for the reversible expansion of one mole of an ideal gas from a volume of 10 litres to 20 litres at 25ºC is A) 2.303 x 298 x 0.082 log2 B) 298 x $10^{7}$ x 8.31 x 2.303 log2 C) 2.303x298x 0.082 log0.5 D) 8.3 1 x $10^{7}$ x 298 - 2.303 log 0.5 View Answer Report DiscussAnswer: Option BExplanation:W = 2.303nRTlog$\frac{v_{2}}{v_{1}}$ =2.303 x 1 x 8 .314 x $10^{7}$ x298 log$\frac{20}{10}$ = 298 x $10^{7}$ x 8.31 x 2.303 log2
