Posted by Kyo on October 30, 2007 at 17:36:22:
In Reply to: Answers to (Oct 29) Qns posted by Kyo on October 30, 2007 at 17:34:20:
Q5 (30 Oct 07)
Explain why the blue ppt obtained when aqueous sodium hydroxide is added to aqueous copper(II) hydroxide, dissolves when you add excess aqueous ammonia.
Q6 (30 Oct 07)
At high temperatures, molecular bromine gass dissociates into bromine atoms. A 0.57g sample of Br2 is placed in a 1dm3 flask and heated to 1550 deg C, after which the total pressure at equilibrium is found to be 0.75 atm. Assuming the equilibrium mixture behaves as an ideal gas, calculate the value of Kp at 1550 deg C.
Q7 (30 Oct 07)
A solution of uranium ions, UO2 2+ (aq) is yellow. The UO2 2+ (aq) are reduced by zinc powder in acidic conditions to green U x+ (aq) ions. The U x+ (aq) ions can be oxidized to UO2 2+ (aq) by acidified MnO4-(aq). It was found experimentally that 20.0 cm3 of 0.10 mol/dm3 of U x+ (aq) ions reacted with 16.0 cm3 of 0.05 mol/dm3 of MnO4-(aq). Calculate the value of x.
Q8 (30 Oct 07)
Calculate the enthalpy change for the reaction N2O3 (g) + N2O5 (s) -> 2 N2O4 (g), given :
NO(g) + NO2(g) -> N2O3(g) ÄHr = -39.8 kJ/mol
NO(g) + NO2(g) + O2(g) -> N2O5(g) ÄHr = -112.5 kJ/mol
2NO2(g) -> N2O4(g) ÄHr = -57.2 kJ/mol
2NO(g) + O2(g) -> 2NO2(g) ÄHr = -114.2 kJ/mol
N2O5(g) -> N2O5(s) ÄHr = -54.1 kJ/mol
Q9 (30 Oct 07)
Calculate the volume of 0.02 mol/dm3 KMnO4 solution required for the complete oxidation of 0.1g of iron(II) ethanedioate (IUPAC name) or iron(II) oxalate (common name).
Q10 (30 Oct 07)
A solution containing ammonium polytriovanadate(V), NH4VO3, in dilute H2SO4 can be reduced by zinc to give a lilac-coloured solution. A 25cm3 portion of a solution containing 0.05 mol/dm3 ammonium polytriovanadate(V) was reduced by zinc and subsequently re-oxidized to the original state using 37.5 cm3 of 0.02 mol/dm3 KMnO4 solution. Calculate the oxidation state of vanadium in the lilac-coloured solution.