A model explaining that chemical reactions occur only when reactant particles collide with sufficient kinetic energy (at least equal to the activation energy) and in.
Molecules must hit each other the right way and hard enough for bonds to break.
Showing a random 20 of 50 problems.
Example 1
medium
Why are gas-phase reactions usually faster than the same reaction in solid form at the same temperature?
Example 2
medium
A reaction speeds up when both temperature and concentration are raised. Separate which factor changes collision energy and which changes collision frequency.
Example 3
easy
True or false: increasing surface area changes the energy of collisions.
Example 4
easy
Most collisions between reactant molecules do not produce a reaction. True or false?
Example 5
medium
Reaction P has Ea=80kJ/mol; reaction Q has Ea=40kJ/mol. At the same temperature, which is faster and why?At the same temperature, which reaction — P (taller barrier) or Q (shorter barrier) — proceeds faster?
Example 6
hard
Use the Arrhenius idea: at T1 the rate constant is k1, at T2>T1 it is k2. Why is k2>k1 when Ea>0?
Example 7
hard
A heterogeneous catalyst works by providing a surface where reactants adsorb. Which two collision-theory factors does this improve?
Example 8
easy
Why do powdered solids react faster than a single lump of the same mass?
Example 9
hard
Why does adding a catalyst speed up a reaction even at very low temperature when very few molecules have Ea energy?
Example 10
challenge
At room temperature very few molecules exceed Ea, yet heating 20°C can double the rate. Explain using the energy distribution.
Example 11
medium
Why does grinding zinc into a powder make it react faster with HCl than a single piece?
Example 12
medium
Why does increasing temperature speed up a reaction far more than the small rise in collision frequency alone would explain?
Example 13
medium
Catalyst C lowers Ea from 75kJ/mol to 50kJ/mol. Does the equilibrium constant (or final yield) change?
Example 14
medium
Explain, using collision theory, why food spoils slower in a refrigerator.
Example 15
easy
Does raising temperature increase or decrease the fraction of collisions that have enough energy to react?
Example 16
medium
Compare reactions of H2+Cl2 (small linear molecules) vs C20H42+Cl2 (long chain). Which is expected to have a higher steric (orientation) factor and why?
Example 17
challenge
Two reactants are very dilute and at low temperature, yet the reaction is fast. Which single change to collision conditions could explain this, and why?
Example 18
medium
Why is the rate of a reaction usually highest at the start and slows as time passes?
Example 19
medium
Why does a catalyst speed up a reaction even though the reactant concentrations are unchanged?The catalyst lowers Eₐ so more collisions clear the barrier — no extra particles needed.
Example 20
medium
Using collision theory, explain why a finely ground powder reacts faster than a large chunk of the same solid.