Increasing the temperature of a reaction generally increases its rate because particles:
Collide more often and with more energy
Become larger
Lose kinetic energy
Stop moving
Tap an answer to check it.
WhyAt higher temperature particles move faster and a greater proportion have energy above the activation energy, so there are more frequent and more energetic successful collisions.
2Multiple choice · Easy
A catalyst increases the rate of a reaction by:
Providing a pathway with lower activation energy
Increasing the activation energy
Raising the temperature
Being used up in the reaction
Tap an answer to check it.
WhyA catalyst provides an alternative reaction pathway with a lower activation energy, so more collisions are successful.
3Multiple choice · Medium
According to collision theory, a collision will only lead to reaction if the particles have:
Sufficient energy and correct orientation
Low energy and any orientation
Equal masses
The same charge
Tap an answer to check it.
WhyAn effective (successful) collision requires both sufficient energy (greater than or equal to the activation energy) and the correct orientation.
4Multiple choice · Medium
Breaking a solid reactant into a powder increases the reaction rate because it:
Increases the surface area
Decreases the temperature
Raises the activation energy
Reduces the concentration
Tap an answer to check it.
WhyPowdering increases the surface area of the solid exposed to the other reactant, so more collisions occur per second.
5Multiple choice · Medium
On a Maxwell-Boltzmann distribution, raising the temperature shifts the peak:
To higher energy and lower height
To lower energy and higher height
Vertically only
It does not change
Tap an answer to check it.
WhyAt higher temperature the distribution broadens and the peak shifts to higher energy (and lower height), so more molecules exceed the activation energy.
6Multiple choice · Hard
Which method could be used to follow the rate of a reaction that produces a gas?
Measuring the volume of gas collected over time
Measuring the colour of the flask
Weighing the catalyst only
Counting the number of bubbles by eye once
Tap an answer to check it.
WhyMeasuring the volume of gas collected (or the loss in mass) over time allows the rate of a gas-producing reaction to be monitored.
7Fill in the blank · Easy
The minimum energy that colliding particles must have in order to react is called the energy.
Answer:
activation / activation energy
WhyThe activation energy, $E_{a}$, is the minimum energy needed for a successful collision.
8Fill in the blank · Medium
A substance that speeds up a reaction without being consumed overall is called a .
Answer:
catalyst
WhyA catalyst speeds up a reaction by lowering the activation energy and is regenerated, so it is not used up.
9Multiple choice · Medium
Why does increasing the surface area of a solid reactant increase the rate of reaction?
More particles are exposed, increasing collision frequency
The activation energy is lowered
The enthalpy change becomes more negative
The equilibrium constant increases
Tap an answer to check it.
WhyMore surface area exposes more particles, increasing the collision frequency.
10Multiple choice · Easy
Collision theory states that a reaction occurs only when particles collide with sufficient energy and the correct
orientation
colour
mass
pressure
Tap an answer to check it.
WhyParticles must collide with energy at least equal to the activation energy and with the correct orientation.
Ready to test yourself?
Practise How fast? The rate of chemical change with instant marking and per-topic score tracking.