1. Using the reactions listed, what property of each method (spectrometric metho
ID: 1003457 • Letter: 1
Question
1. Using the reactions listed, what property of each method (spectrometric methods, conductometric methods, and manometric methods) resulted in the selection of the specific method that was chosen? (explain your answer)
NO (g,colorless)+O3(g,colorless) yields O2(g,colorless)+NO2(g,brown)
(CH3)3-Br(l)+H2O(l) yields (CH3)3C-OH(l)+H^(+) (aq)+Br^(-) (aq)
2H2O2(aq) yields 2H2O(l)+O2(g)
2. write the relative rate expressions in terms of the appearance of each product and the disappearance of each reactant: (show your works)
a. dinitrogen pentoxide yields nitrogen + oxygen
b. hypochlorous acid + delta(heat) yields chloric acid + hydrochloric acid
c. write the balanced equation for the compusion of n-propane, C3H8(g)
d. if the concentration of n-propane in part (c) is changing at the rate of 0.25M/sec, what are the rates of change of the other three reactants and products?
Explanation / Answer
1. NO (g,colorless) + O3(g,colorless) yields O2(g,colorless)+NO2(g,brown)
To study the reaction spectrometric method can be used. Colored products strongly absorbs light at a particular wavelength. As NO2 is the only colored substance in the reaction, this reaction can be studied by spectrometric methods.
(CH3)3-Br(l)+H2O(l) yields (CH3)3C-OH(l)+H^(+) (aq)+Br^(-) (aq)
The reactants do not carry electricity as they do not form ions. But the products conduct electricity due to the formation of ions. So this reaction can be studied by the change of conductance of the reaction mixture, hence conductometric methods should be used.
2H2O2(aq) yields 2H2O(l)+O2(g)
As the reaction proceeds gaseous oxygen is formed, as a result of this pressure of the system increases (if carried out in a closed vessel). This reaction can be studied by manometric methods.
2. (A)
2N2O5 = 2N2 + 5O2
relative rate expressions:
-[N2O5]/2t= [N2]/2t= [O2]/5t
This indicates that, rate of formation of N2 is same as the rate of disappearance of N2O5. And rate of formation of O2 is 5/2 folds as fast as the disappearance of N2O5.
(b) 3HClO = HClO3 + 2HCl
relative rate expressions:
-[HClO]/3t= [HClO3]/t= [HCl]/2t
(c) C3H8 + 5O2 = 3CO2 + 4H2O
relative rate expressions:
-[C3H8]/t= -[O2]/5t =[CO2]/3t= [H2O]/4t
(d) concentration of n-propane is changing at the rate of 0.25M/sec,
-[C3H8]/t = 0.25M/sec
So, -[O2]/t = 5* -[C3H8]/t = 1.25M/sec
[CO2]/ t = 3* -[C3H8]/t = 0.75M/sec
[H2O]/t = 4* -[C3H8]/t = 1.00 M/sec
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