# Chemistry Unit2 - fill in the gaps

This document contains a couple of pages of notes where you have to fill in the gaps, it helps you to remember things rather than just reading them. It covers energy, rates of reactions, electrolysis, acids and alkalis, reversible reactions in short simple sentences that will help you revise unit2 (...hopefully!!)

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Chemistry Unit 2 ­ Quick Revision Notes
The ____ of a reaction is measured as either the amount of ________ used up in a given
time or the amount of _______ formed in a given time.
In order for a reaction to occur, the particles must _______.
If more collisions can be made to take place in a given time, the rate of the reaction will
________.
Some collisions don't lead to a reaction taking place. Only collisions with sufficient ______
can lead to a successful reaction. So, if we can increase the _______ rate of the collisions,
this will also lead to an increase in the rate of reaction.
The minimum energy that must be possessed by the particles for the collision to be
successful is called the __________ energy.
Increases in c____________, p_______ of gases and s______ a___ of solids all lead to
more collisions taking place per second.
Increase in t__________ leads to more collisions per second but also collisions that have,
on average, a greater energy so the success rate is higher too.
_________ lower the activation energy by providing an alternative route and so the success
rate is higher.
Catalysts are usually ________ to a particular reaction. They are very important in a
number of industrial processes.
______________ are usually measured in units of mol dm3 (moles per litre).
_____ volumes of gases at the same temperature and pressure contain the ____ number
of molecules (and moles) of gas.
Energy and reactions When chemical reactions occur there is an ______ exchange with the
surroundings.
If heat is given out to the surroundings, it is said to be an __________ reaction, if heat is
absorbed from the surroundings it is said to be an ___________ change. Beware, if a
reaction "gets hot" it may seem like it is absorbing heat from outside but really it is the
chemicals reacting, giving their heat energy to the water or container etc and then the heat
If a reaction can go in both forward and backward directions it is called a _______ reaction.
If the forward direction is e_othermic, the reverse direction must be equally ___________. If
the forward reaction is endothermic, the reverse must be equally __________.
If the system is ______ (ie substances can't escape or be added), a reversible reaction can
come to ___________.
At equilibrium, the forward and reverse reactions keep going but at the ____ _____ so that
there is no overall change.

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### Page 2

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The equilibrium position can be adjusted by changing conditions of temperature and
pressure. This can be used to our advantage in industry.
An ________ in temperature favours the endothermic direction.
An ________ in pressure favours the direction with a decrease in the number of moles of
gas.
The conditions for reversible reactions in industry also take into account the needs to have
a good rate and a minimal cost.
A __________ is sometimes needed.…read more

### Page 3

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A low pH means that there is a ____ concentration of H+(aq) ions (hydrated protons) and so
the solution is strongly ______.
A high pH value means that the solution has a high concentration of OH(aq) ions (hydrated
hydroxide ions) and so is strongly alkaline.
Neutralisation is the reaction between __ (aq) and ___ (aq) to form water.…read more
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