Easy MC Question (1 Viewer)

[J-Wang]

Can someone please explain the calculation steps to me in this? I understand it should be really easy, but I'm just not getting it atm
http://www4.boardofstudies.nsw.edu....wer=C&courseID=15050&testQuestionID=301801752
And also; http://www4.boardofstudies.nsw.edu....wer=D&courseID=15050&testQuestionID=301801755

 

[Yindi]

you're given a mass, but the answers are all in litres.

from the graph you have 8mgL^-1
you have 10 L, therefore 80mg

n = m/M = (80*10^-3)/(32) oxygen is diatomic therefore molecular mass = 16 + 16
n = 2.5*10^-3 Mol

therefore V = n * 24.79 = 61.975 *10^-3 L = 62 mL

not so easy after alll hey...

 

[J-Wang]

you're given a mass, but the answers are all in litres.

from the graph you have 8mgL^-1
you have 10 L, therefore 80mg

n = m/M = (80*10^-3)/(32) oxygen is diatomic therefore molecular mass = 16 + 16
n = 2.5*10^-3 Mol

therefore V = n * 24.79 = 61.975 *10^-3 L = 62 mL

not so easy after alll hey...

Ahhhhhhh that was my problem. I knew to do the rest, I just forgot Oxygen was diatomic so I went back to my last correct step which was 80 lol

 

[Yindi]

Haha it's a common error but now you won't make it on tuesday!!

 

[J-Wang]

I got the second one. Don't worry about it