Sciencemadness Discussion Board

oleum

zab30 - 25-1-2016 at 07:08

Can anybody tell very simply how much so3 by weight needs to be added to 96% sulfuric acid before it can be called 20% oleum

Tsjerk - 25-1-2016 at 07:33

Do you know the densities of 96% H2SO4 and 20% oleum?

woelen - 25-1-2016 at 07:44

It looks like this is homework.

I assume the percentages are by weight. In that case, proceed as follows:

Take 96% H2SO4. Take 100 grams of this. You have 4 grams of water. How many grams of SO3 is needed to make H2SO4 of that water? How many grams of H2SO4 do you have in that situation? Now you add an additional amount of SO3, so that 20% of the total weight is SO3 and the remaining part is H2SO4. This is NOT accomplished by adding 20% of that weight of SO3, you need to add more SO3.

If you want to compute e.g. how many grams of SO3 are needed to convert 100 ml of 96% H2SO4 to 20% oleum, then you need the density of 96% H2SO4 as well. Density of 20% oleum is not needed in your computations.