Chemistry topic 2

What is a mole?

The amount of a substance that contains as many particles as there are atoms in 12g of C-12

What is Avogadro's constant?

The number of particles in one mole of a substance is always the same.

How do you find the number of moles?

Number of moles = mass(g) / Mr

How do you find the number of particles?

Number of particles = number of moles * Avogadro's constant

How do you find atom economy?

Atom economy= ( Mr of desired product/ Mr of all products) * 100

Why do you carry out titrations?

To know the concentration of an acid that is needed to neutralise a known volume of an alkali, or vice verse.

What type of pipette is used in titrations and why?

Volumetric pipette - delivers fixed volumes.

What must you do before carrying out a titration?

Clean out burette with whatever substance you are putting into it to ensure no other reactions happen.

Why do you do a rough titre?

To find more specific results by slowing down near to the value during repeats to ensure concordent results.

What indicators can be used and what colours are they when in an acid and an alkali?

1. Methyl orange - acid: Red, alkali: Yellow

2. Phenolphthalein - acid: colourless, alkali: Pink

How do you find a concentration?

Concentration= moles / volume

What is a standard solution?

A solution with a specific/known concentration.

How do you make a standard solution?

1. Weigh the solute - mass by difference.

2. Dissolve the solute.

3. Make up solution to known volume.

4. Homogenise the solution. - make sure the solute is fully dissolved.

Why do you use standard solutions?

• Accurate results - known concentration.

• Calibration - calibrate equipment in lab setting.

• Consistency

What is ideal gas?

F