Question

Question:1 In the introduction of this experiment, there are several factors that are discussed as having an impact upon the rate of a reaction. Pick one of these factors and come up with an original idea (not from the experiment or lecture) where the factor plays a role in the rate at which a chemical reaction occurs. Be sure to explain how and why your idea affects the rate of the reaction chosen. For example: if you increase the surface area of a piece of coal by crushing it up, it will react with oxygen (burn) much more rapidly. This illustrates the relationship between surface area and reaction rate. Question:2 There is a general rule of thumb that the rate of an observable chemical reaction doubles with every 10oC increase in temperature. How much would the rate of a chemical reaction change if the temperature were to increase by 80.0oC? Be sure to show your work.

Answer 1

Q.1: A peace of coal or a peace of wood doesn't burn at normal temperature. When we start increasing the temperature, the activation energy for the combustion of coal is gradually achieved and the rate of the reaction gradually increases and the coal start burning at a faster rate.

We can give another example as at room temperature on troposphere the decomposition of O3 to O2 is very slow. However as we move to ionosphere the atmospheric temperature increases and hence the rate of decomposition of of O3 to O2 increases many fold.

Q.2: When we increase the temperature the rate constant increases and hence the rate of reaction increases.

Let's consider a chemical reaction with activation energy, Ea = 46 KJ/mol = 46000 J/mol

Suppose at T1 = 300K, the rate constant be 'k'

When the temperature increases by 80 DegC, T2 = 380 K.

Now the rate constant, k2 at 380K can be calculated from Arrhenius quation as

ln(k2 / k) = (Ea/R) x [1/T1 - 1/T2] = (46000J.mol-1 / 8.314 J.mol-1.K-1) x [1/300K - 1/380K]

=> ln(k2 / k) = 3.8827

=> k2/k = 48.6

=> k2 = 48.6 k

Hence the rate of reaction increases by 48.6