Gases Flashcards
How do volumes of gases react with each other if they are measured in the same temperature and pressure?
In the same whole number ratio
Avogadro’s law
Equal volumes of gases under the same conditions of temperature and pressure contain the same number of molecules
No matter the gas
Why is Avogadro’s law useful?
So we can do gas calculations without finding mass (which is difficult) but finding volumes instead which is easier
How does Avogadro’s law apply to reacting ratios?
We can find the volumes of reacting gases according to ratio due to previous theory
But by Avogadro’s law that equal volumes of gases contain same number of molecules/ moles then we can find number of moles using the ratios as well
How to find the volume of gas(es) at the end of the equation if the volumes react in the same ratio
find the ratio number of the product from the equation then use that to find the volume compared to the volumes of reactants
MAKE SURE to check the product is a gas
if more than one gaseous product then add the volumes together
What’s important to remember about reacting volumes in a ratio?
Only include gases in the ratio (use state symbols and ignore non gases)
the product volume isn’t from adding the reactant volumes together but calculating the volumes of the products from the ratio THEN adding these products together
How can you tell if a gas reactant is in excess?
Look at the reactants ratio then the other reactants volume
Use it to find ideal volume of that gas for both to fully react
If the actual volume we have is more = in excess
How can you tell if a gas reactant is limiting?
Look at the reactants ratio then the other reactants volume
Use it to find ideal volume of that gas for both to fully react
If the actual volume we have is less = limiting
What happens if one of the gas reactants is limiting?
All of the LIMITING reactant will react
According to the ratio, work out how much of the excess gs will react using the amount of limiting reactant
If one of the gases is limiting, what will the total volume of gases be at the end?
any of the product volumes worked out according to ratio
Plus the left over excess reactant gas, worked out by taking away the total we had from what reacted
Molar volume
The volume of gas that contains ONE mole (6.022x10^23 atoms/ molecules) of the gas
Aka the amount of space it will occupy
Which is 24dm3 mol-1
What is the molar volume of all gases?
1 mole of EVERY gas occupies 24dm3
only at room temperature and pressure
why does one mole of any gas occupy 24dm3 at rtp and rp?
Because according to Avogadro’s law the same volume of any gas has the same number of molecules/atoms
and so if this number of molecules/atoms is one mole (eg 6x10^23) then the volumes of the gas will be equal. this volume is 24dm3)
Calculation for moles/ volume?
Volume a gas occupies = 24 x number of moles
Because one mole of any gas occupies is 24dm3
Symbol for molar volume
Vm
