1.) Activation energy is _____.
2 answers:
Answer: 1. B.) the energy barrier between reactants and products
2. C.) increases as reactant concentration increases
Explanation: Activation energy is defined as the extra energy required by the reactants to cross the energy barrier in order to get converted to products.
Activation energy is high for slow reactions and low for fast reactions.
Heat released in a reaction is called as the enthalpy change for a exothermic reaction.
2. Rate law says that rate of a reaction is directly proportional to the concentration of the reactants each raised to a stoichiometric coefficient determined experimentally called as order.
Rate of a reaction is increased by a catalyst as it decreases the activation energy and is usually increased by increase in temperature.
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Rate law for the given 2nd order reaction is:
Rate = k[a]2
Given data:
rate constant k = 0.150 m-1s-1
initial concentration, [a] = 0.250 M
reaction time, t = 5.00 min = 5.00 min * 60 s/s = 300 s
To determine:
Concentration at time t = 300 s i.e.
Calculations:
The second order rate equation is:
substituting for k,t and [a] we get:
1/[a]t = 0.150 M-1s-1 * 300 s + 1/[0.250]M
1/[a]t = 49 M-1
[a]t = 1/49 M-1 = 0.0204 M
Hence the concentration of 'a' after t = 5min is 0.020 M