What is relative formula mass
All the relative atomic mass of elements in that compounded added togtehrr
What does one mole of each element contain the same number of
Particles
What is different in a mole of different elements
Mass
Equation to find moles
Mass / Mr
Empirical formula definition
Simplest whole number ratio of elements in that compound
Steps to find empirical formula
Calculate moles of each element
Divide no of miles by the smallest number
Find nearest whole number ratio
Write formula
How to find molecular formula from empirical formula
- Calculate MR of empirical formula
- Calculate Mr of molecular formula
Find the ratio
Times empirical formula by ratio
method for experiment combustion of magnesium
Weigh crucible and lid and record mass
Rub surface of around 5cm of magnesium ribbon with sandpaper to clean and remove and oxidised
Weigh crucible lid and magnesium
Heat crucible on roaring flame on a triangle with a Bunsen burner
Open lid every so often to let in air without letting smoke escape
When the reaction appears to be over continue to heat strongly for 2-3 minutes and weigh crucible lid magnesium oxide
How to use magnesium combustion experiment to find empirical formula
Calculate mass of magnesium from crucible lid magnesium - crucible and lid
Calculate mass of magnesium oxide from crucible lid magnesium oxide - crucible lid
Calculate mass of oxygen from magnesium oxide - magnesium
Use masses of magnesium and oxygen to find empirical forums
Why do students calculate a lower amount of oxygen than magnesium during the magnesium combustion experiment
When lifting the crucible lid, they allow the magnesium oxide powder to escape and therefore have a lower mass of magnesium oxide + lid + crucible. This means that the calculated mass of oxygen is lower.
The magnesium may also not be properly cleaned and may have already oxidised or reacted before staring the experiment
Why do you lift the lid in the magnesium combustion reaction
To let oxygen into the crucible, to ensure there is a good oxygen supply
Why should you not lift the lid for too long in the magnesium combustion experiment
To not allow the magnesium oxide powder to escape and avoid looking at the bright white light
Why do some methods tell you to heat the magnesium oxide in the magnesium combustion experiment until you get a consistent mass
Ensures all the magnesium has reacted
What is the purpose of the reduction of copper oxide experiment
Find the empirical formula of an oxide of copper
Method for copper oxide reduction
Weigh an empty reduction tube
Add two spatulas of copper oxide into the tube (in horizontal position)
Set up a methane supply going into the bung, a Bunsen burner below the copper oxide and a horizontal reduction tube
Allow methane to flow through the tube then light
Heat strongly on roaring flame
When the colour change to red brown appears complete stop heating but keep methane flame burning
Turn off the flame when tube is cool and weigh tube
Heat for further two minutes
Repeat final two steps until constant mass is reached
why is methane allowed to flow through the tube before being lit in copper reduction
To flush out the air and oxygen and ensure a sufficient methane supply
Why is methane allowed to flow through the tube until the apparatus has cooled in the copper reduction
To not allow oxygen into the air to enter and react with the hot reactive cu
What is methane in copper reduction
Reducing agent
Name of process when water is evaporated from crystals by heating
Dehydration
Method for water of crystallisation experiment
Using a beaker to hold the boiling tube weigh the mass of an empty boiling tube
Add in around 5g of hydrated copper sulphate into the boiling tube (note precise mass of copper sulphate added)
Gently heat the copper sulphate using a test tube holder
When the colour change from blue to white appears complete wait for the tube to cool then weigh
