### 1.why does the rate of a reaction not remain constant throughout the reaction process? 2. the slope of the line for the graph of Log k v/s 1/t for the reaction N2O5->2NO2 +1/2 O2 is -5000. find activation energy. 3. how much time is required for 3/4th of PH3 to decompose

1. The rate of the reaction always depends upon the concentration of reactants/products per unit time.
That is, rate of reaction = Decrease in conc. Of reactants per unit time
or
Increase in conc. Of products per unit time
Factors that affects the rate of a reaction are ;
1. Nature of reactants
2. Concentration of reactants
3. Surface area of the reactants
4. Temperature
5. Catalyst and
6. Light

2. The slope of the line for the graph of log k Vs 1/t for the reaction
N2O5 ? 2 NO2 + 1/2 O2 is – 5000

find activation energy.
According to Arrhenius equation

Taking logarithm

When we plot log k Vs 1/t we get a standard line of slope equal to

and the intercept equals to log A.

Ea = - 2.303 R x slope
= - 2.303 x 8.314 x – 5000
= 95735 j mol-1 or
Ea = 95.735 kj mol-1

3. It belongs to I order reaction and the rate constant is

By knowing the rate constant, k we can find out 't'.