chemistry doubt

[jesse d]

9701/11/ON/14 qp 15. A sample of pottasium oxide is dissolved in 250cm3 of distilled water. 25cm3 of this solution is titrated against sulfuric acid of concentration of 2.00moldm3. 15cm3 of this sulfuric acid is needed for complete combustion. Which mass of pottasium oxide was originally dissolved in 250cm3 of distilled water. Ans is 28.3g. Please help

 

[Metanoia]

K2O + H2O --> 2KOH ------- (1)

2KOH + H2SO4 --> K2SO4 + 2H2O ----(2)


moles of H2SO4 used in (2) = conc x vol = 2 x 0.015 = 0.03 mol
moles of KOH used in (2) = 0.03 x 2 = 0.06 mol

Taking into account the dilution factor,
moles of KOH in 250 cm3 = 0.06 x 10 = 0.6 mol
moles of K2O = 0.6/2 = 0.3 mol

mass of K2O = 0.3 x Mr


Its better to post your doubts in this thread for faster response.
https://www.xtremepapers.com/community/threads/chemistry-post-your-doubts-here.9859/page-659

 

[jesse d]

thanks. Im new here. I dnt know things work, thanks for the insight