titration problem (1 Viewer)

[smallcattle]

HSC 2003 Q23

25 mL of 0.12 mol/L barium hydroxide titrated with nitric acid

1. 20.4 mL
2. 18.1
3. 18.2
4. 18.1

whats the concentration of nitric acid??

and also i thought the variation between each test should be 1.5mL right??? cuz i remember i even lost a mark in a prac due to great variations

 

[Paroissien]

Yeah, I'm quite sure you would discard the 20.4mL result leaving you with an average titre of... lets say 18.1mL
Ba(OH)2 + 2HNO3 ---> Ba(NO3)2 + 2H2O
moles = molarity * mls/1000
moles (BaOH2) = 0.12 * 25/1000
= 0.003 moles of BaOH2
moles (HNO3) = 2* moles (BaOH2)
moles (HNO3) = 0.006
moles = molarity * mls/1000
molarity = moles / (mls/1000)
= 0.331 moles/L of HNO3

 

[tennille]

That's the answer- i saw it on the marking guidelines. You discard the first because it differs greatly from the other 3. I'm assuming that was a trial one.

 

[Xayma]

No the measurements you use for your average should be within 0.1mL, pretty much within a drop.

 

[Paroissien]

BTW is there any way to do subscript and superscript on the forums?