GCSE C5.1

Monitoring chemical reactions

What is concentration?

A measure of how much of a substance is present in a given volume

Units of concentration?

g/dm³ or mol/dm³

How can concentration be calculated?

Concentration (g/dm³) = Mass / volume Concentration (mol/dm³) = Moles / volume

How can you increase the concentration of HCl?

Decrease the volume of the solution Increase the number of moles of HCl

Cm to dm

divide by 1000

What is the molar volume of a gas?

the volume occupied by one mole of a gas at room temperature and pressure

What is RTP?

Room temperature and pressure:

• 20oC

• 1 atmosphere

What is the molar volume of gas at RTP?

24 dm^3

What is yield?

The amount of product you get from a reaction

Why do you never get 100% yield?

• some reactants may be left behind in the equipment

• there may be side reactions where a substance reacts with a gas in the air

• the reaction may be reversible and the products are continually turning back into the reactants

What is the theoretical yield?

the amount of product that would be obtained under perfect conditions

What is the percentage yield?

a good way of measuring how successful a chemical process is a high percentage yield to increase profits and reduce costs/waste

Percentage yield equation

actual/theoretical x100

Atom economy

(Molecular mass of desired products/ Molecular mass of all products) x 100

What is an atom economy used for?

to analyse the efficiency of reactions

The higher the atom economy...

the more sustainable

What does atom economy study?

The amount of reactants that get turned into useful products

What reactions are unwanted

Those with low atom economies - unsustainable

What is desirable?

High percentage yields and fast reaction rates

Equipment needed for titrations

• burette

• pipette and pipette filler

• conical flask -white tile

• funnel

• clamp and stand

What are concordant results?

Results within 0.1 cm³ of each other

What are titrations?

A method of analysing the concentrations of solutions. Used to determine exactly how much alkali is needed to neutralise a quantity of acid

What are indicators in titrations used for?

To show the endpoint in a titration

Why is universal indicator not suitable in a titration?

It gives a range of colours and not a sharp endpoint

Why is litmus not suitable in a titration?

the colours are similar