Year 12s: what will be the first way you research your future options? >>

Concentration Help - AS

Would anyone be willing to answer some concentration questions on page 4 of the exam paper. I have answered all of them correctly except question e)v) the last part where it gets a bit confusing for me.

http://www.scribd.com/doc/79256965?secret_password=lh4oog7hqi4oynpdlvy

Reply 1

clownfish

i) burette
ii) n=conc x vol = 0.05 x (26.4/1000) = 1.32x10-3moles (remember to always divide cm3 by 1000 to get dm3)
iii) 2:1 ratio so 6.6x10-4 moles H2SO4 in 20cm3
iv) conc = mol/vol = 6.6x10-4 / (20/1000) = 0.033 moldm-3
v) But this was a watered down sample from 10cm3 to 250cm3, so the original concentration was 25x more. so 0.825 moldm-3