We know from yr 11 that:
This can be explained by the following equation, the ideal gas law: $$PV=nRT \text{ or } P=\frac{nRT}{V}$$
These are the units for the equation:
$P$ - Pressure - $kPa$
$V$ - Volume - $L$
$n$ - Number of moles - $mol$
$T$ - Temperature - $Kelvin$
$R$ - Gas constant - On the data sheet, but it is 8.314 units (generally).
e.g. Assume standard temperature and pressure:
$$\begin{align} 100\times V = 1 \times 8.314 + 273.15 \\ \therefore V=22.71L \end{align} $$Recall Degrees $\implies$ Kelvin is +273.15
Very important The course for gas laws before 2015 was much more complicated. Don't need to fret about those questions.
e.g.
Usually, when we are dealing with a $C_{x}H_{y}O_{z}$ molecule, we can combust it.
The residual $CO_{2}$ and $H_{2}O$ can be measured, and we can use this to deduce how much was in the original substances(their molar ratios).
We are given this information through many ways (percentage, mass)
Once we have analysed/worked out the quantities in a sample, we want to make a table, where headings $\implies$ things we know are present in the substance, and somehow we are going to get to the number of moles.
Then, we want to divide by the smallest number of moles.
Next, we want to approximate to whole number ratios.
This gives us an empirical formula.
We may be given extra information, which we want to use to find molar masses.
We can then use molar masses to determine the molecular formula!
There may be hints as to what it could be.
