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Question
Mention the factors that affect the rate of a chemical reaction.
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Solution
(i) Nature of the reactant: The rate of reaction depends on the nature of the reactant. For example, ionic molecules react more quickly than covalent ones.
(ii) State of reactants: Solid reactions are slower, liquid reactions are faster, and gas reactions are very quick.
(iii) Temperature: The rate of reaction is mainly affected by temperature. Every 10°C rise in temperature increases the reaction rate by 2-3 times.
`(r_(t + 10))/r_t` = 2 − 3
This ratio is called the temperature coefficient.
There are two reasons why the reaction rate increases with temperature.
- Increasing temperature raises the average kinetic energy of reactant molecules, increasing the rate of collisions.
- As the temperature rises, the number of molecules with threshold energy increases, resulting in more active molecules. As a result, the number of effective collisions grows. As a result, the reaction rate increases.
(iv) Concentration: The rate of reaction depends on the concentration of reactants.
Rate = k × Cn
Where,
n = order of reaction
C = concentration of reactant
(v) Catalyst: The presence of a catalyst changes the rate of the reaction. It lowers the activation energy by producing a chemical intermediate, lowering the potential energy barrier. Thus, the reaction rate increases.
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- How order and molecularity are different for complex reactions? [1]
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OR
The half-life for radioactive decay of 14C is 6930 years. An archaeological artifact containing wood had only 75% of the 14C found in a living tree. Find the age of the sample.
[log 4 = 0.6021, log 3 = 0.4771, log 2 = 0.3010, log 10 = 1] [2]
