Slides in this set

Slide 1

Preview of page 1

Chemistry 3b
Moles and titration
Titration calculations
Energy and Fuels
Bond Energies
Getting energy from hydrogen
Tests for positive ions
Tests for negative ions…read more

Slide 2

Preview of page 2

Moles and titration
When you have one mole of a substance, its mass in grams is equal to its relative
atomic mass. E.g. one mole of carbon12 weighs 12g. One mole of a substance is 6.023
The concentration of a solution can be measured in moles per dm³ or in grams per
*1 litre = 1000cm³ = 1dm³
The more solute that's added to a given volume, the more concentrated the solution
Titration calculations can be used to figure out how much of an acid or alkali is needed
to neutralise a solution..…read more

Slide 3

Preview of page 3

Moles and titration
An alkali should be put inside of the conical flask with an indicator.
We don't use universal indicator in titration because it changes
colour too slowly. Instead we use phenolphthalein or methyl
Acid is placed inside the now closed burette.
The acid is dripped into the alkaline solution one drop at a time, and
the contents of the conical flask is stirred constantly.
When the indicator has changed colour to show that the solution has
been neutralised, you stop adding acid into the solution.
Using the measurements of the burette, record how much acid was
used to neutralise the solution.
Repeat the experiment multiple times, to make sure that the results
are reliable and reproducible. You can then find a mean of these
results.…read more

Slide 4

Preview of page 4

Titration calculations
Concentration in moles per dm³:
Figure out how many moles of the known concentration there are
Number of moles = concentration x volume
*If you're given the volume in cm³, remember to convert it into dm³ by dividing
it by 1000.
Find the proportions of the equation (like if for every two moles of the first
substance there is one mole of the second substance)
You can then figure out how many moles of the unknown substance there are
Work out the concentration of the unknown substance
Concentration = number of moles / volume…read more

Slide 5

Preview of page 5

Titration calculations
Concentration in grams per dm³:
Find out how many moles of each substance there are
Figure out the relative formula mass of the unknown substance
Convert the concentration in moles (that you've already worked out), into
concentration in grams
Mass in grams = moles x relative formula mass
I don't understand this.…read more

Slide 6

Preview of page 6

The amount of energy that's released in a chemical reaction can be measured by
measuring the starting temperature of the reactants (making sure that they're the
same), mixing them in a polystyrene cup and measuring the temperature of them
after the reaction has taken place.
A problem with energy measurements is that a lot of energy can be lost to the
surroundings. The effect of this can be reduced by putting the polystyrene cup into a
beaker of cotton wool for added insulation. A lid could also be put onto the cup to
reduce how much energy is lost by evaporation.
This method of measuring energy transfer works for reactions where solids are
reacted with water, and for neutralisation reactions.…read more

Slide 7

Preview of page 7
Preview of page 7

Slide 8

Preview of page 8
Preview of page 8

Slide 9

Preview of page 9
Preview of page 9

Slide 10

Preview of page 10
Preview of page 10


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »