Posted by Kyo on October 30, 2007 at 17:40:35:
In Reply to: Ans to (Oct 30) Qns posted by Kyo on October 30, 2007 at 17:37:20:
Q11 (31 Oct 07)
300 cm3 of a mixture of dinitrogen monoxide and nitrogen dioxide at r.t.p conditions is bubbled through 75 cm3 of 0.1 mol/dm3 acidified hydrogen peroxide solution. The nitrogen dioxide is oxidised to nitrate(V) ions while dinitrogen monoxide does not react at all. The remaining hydrogen peroxide in 50cm3 of the resulting solution is then titrated with a 0.05 mol/dm3 KMnO4 solution, of which 22 cm3 was required. Calculate the % by volume of dinitrogen monoxide in the mixture.
Q12 (31 Oct 07)
The following refers to an equilibrium reaction.
2A (g) + B (s) <---> C (g) + 3D (g)
When 1.2 mol of A was reacted with 1.0 mol of B in a 2.0 dm3 vessel to form C and D, it was found that 30% of A had been converted. Calculate Kp for this reaction.
Q13 (31 Oct 07)
Nitroyl fluoride undergoes decomposition with the following mechanism :
NO2F (g) --> NO2 (g) + F (g)
NO2F (g) + F (g) --> NO2 (g) + F2 (g)
a) Using Lewis / Kekule structures, draw the step-by-step (ie. electron flow) mechanism for the reaction.
b) By deducing and explaining which is the rate determining step, write the rate equation, and state the units of k.
c) Sketch the graph of (i) concentration of nitroyl fluoride against time, and (ii) concentration of nitrogen dioxide against time, highlighting any special feature(s) in each graph.
d) At 30 deg C, nitroyl fluoride gives 80 cm3 of nitrogen dioxide on complete decomposition, and 40 cm3 of nitrogen dioxide in 40 minutes at the same temperature. Find the time taken for 70 cm3 of nitrogen dioxide to be evolved at the same temperature.
Q14 (31 Oct 07)
For 100 minutes, an 8 ampere current is passed through an aqueous solution of chromium(III) oxide. Calculate the total volume of gas(es) evolved at standard temperature and pressure.
Q15 (31 Oct 07)
Describe and explain, with labelled diagrams, how the value for the Avogadro constant could be determined by electrolysis.
Q16 (31 Oct 07)
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