propene and steam react to form propan-2-ol. If the yield is 75% what mass of propene is required to produce 410g of propane-2-ol. [molar masses/gmol-1 propene=42, propan-2-ol =60]

remember the equation moles = mass/molar mass. We have the final grams of product and also the molar mass so we can calculate the number of moles we got from this. [410/60=6.83moles] It is asking for a 75% final yeild so we know 75% corresponds to 6.83 moles. This is because whatever the actual amount was meant to be we only got 75% of it.It's like when you do an experiment and you get less than you expected.We are told what we actually got but we want to know what we would have got if the experiment was perfect. To do this use the ratio method [ 6.83100/75=9.11mol which corresponds to 100% yeild]. Propene and propane-2-ol are in the same 1:1 ratio in the reaction. (I can help draw this out if needed) Hence all you need to do now is calculate the mass of propene. Use the equation moles=mass/molar mass again with the number of moles as 9.11 and the Mr as 42 [9.1142=383g]