Tutor profile: Dev S.

Q: 70 gms of nitrogen gas was initially at 50 atm and 25°C a) It was allowed to expand isothermally against a constant external pressure of one atmosphere. Calculate, U, Q and W assuming the gas to behave ideally. b) Also find out the maximum work that would be obtained if the gas expanded reversibly and isothermally to one atmosphere.

Solutioon a) Amount of gas n = 70/28 = 2.5 moles Initial pressure; P1 = 50 atm Final pressure P2 = 1 atm R = 8.314J/K/mol =2 cal/K/mol T =(25 +273)K = 298K Since the gas is ideal, U = 0, as the temperature is constant. The work obtained w = P2 (V2 – V1) V2= nRT/P2 & V1= nRT/P1 on solving, w = 1.5 Kcal Solution b) b) The maximum work for its isothermal reversible expansion. W = nRT ln P1/P2 = 2.303 nRT ln P1/P2 on solving, W = 5.8 Kcal

Which of the following has the most acidic hydrogen ? 1. 3-Hexanone 2. 2, 4-Hexanedione 3. 2, 5-Hexanedione 4. 2, 3-Hexanedione

Answer is b) Explanation: H atom at C-3 is sandwiched between to Electron Withdrawing Groups (EWG), ketone C=O at alpha position wrt these groups. Hence resulting conjugate base formed after removal of H atom from C-3 will be most stabilized due -I and -R effect of tow ketone groups.

Q: The Property of hydrogen which distinguishes it from other alkali metals a) Its electropostive character b) Its affinity for non metals c) its reducing character d) its non metallic character

answer is d) its non metallic character