How is the rate of formation of Br2 is related to the rate of disappearance of Br, BrO3 and H+ in the reaction given below:
5Br-(aq)+BrO3-(aq)+6H+(aq)  3Br2(aq)+3H2O(l)

This can be explain by the rate law

Rate = 13dBr2dt=-15dBr-dt=-dBrO3-dt=-16dH+dt
thus form the above rate law explain the formation of Br2 is realated to the rate of disapearance of Br.
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For the reaction: 3H2(g) + N2 (g) → 2NH3(g) express the rate of reaction in terms of
-dH2dt, -dN2dt and dNH3dt.

For the reaction 3H2(g) + N2 (g) → 2NH3(g) 

Rate of reaction = 

13dH2dt=-dN2dt=12dNH3dt.

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How is the rate of formation of NO2 related to the rate of disappearance of NO and O2 in the reaction given below:
                        2NO(g) + O2(g)    2NO2(g)

Formation of NO2 rate of disappearnace of  NO and O2 is given by rate equation:

Rate=12dNO2dt=-12dNOdt=-dO2dt
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For a reaction 2I + 2H+ → I2 (s) + H2(g), if the initial concentration of I–1 was 0.80 mol L–1 and concentration after 20 minutes was 0.68 mol L–1. Calculate the rate of disappearance of I and rate of appearance of I2.

Rate=-12I-t         =-12H+t=I2t=H2t

We have to calculate the rate of disappearance I–1 and rate of appearance of I2, hence

                              Rate=-12I-t=I2t

but                     I-t = Change in concentration of I-Change in time                = (0.68-0.80) mol L-1(20-0) minutes=0.1220=0.006 mol L-1 min-1

We know that  I2t=12I-t=12×0.006 mol L-1 min-1          
                                     =0.003 mol L-1 min-1.
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The gas phase decomposition of acetaldehyde
CH3CHO(g) → CH4(g) + CO(g)
at 680 K is observed to follow the rate expression
rate=-dCH3CHOdt=kCH3CHO1/2
If the rate of the decomposition is followed by monitoring the partial pressure of the acetaldehyde, we can express the rate as
dpCH3CHOdt=kpCH3CHO3/2
If the pressure is measured in atmosphere and time in minutes then
(i) What are the units of the rate of reaction?
(ii) What are the units of rate constant k?


The gas phase decomposition of acetaldehyde

CH3CHO(g) → CH4(g) + CO(g)

at 680 K is observed to follow the rate expression
rate=-dCH3CHOdt=kCH3CHO1/2

Thus,

(i) Units of rate of reaction = 
atmosphereminutes = atm min-1

(ii)   
              Units of k = units of rate(units of pCH3CH)3/2                  = atm min-1atm 3/2=min-1atm1/2 = atm-1/2 min-1                  = bar-1/2 min-1.

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