Adding subjects that aren't showing/Physics Chatter

[simpak]

Yeah it was pretty alright I thought.  I prepared for that question because my friend told me it was on their exam last year, and Geoff Shaw strikes me as someone with better things to do with his time than write new exam questions.  However, I did freeze to death even though I was wearing five layers.

PRESUMING YOU'LL BE AT CHEM TOMORROW: is the oxidation number of Si in the silicate anions/network solids etc always +4 or did I just make that up?

[Russ]

Menstrual cycle is on the exam of every subject that ever teaches it, it's so...perfect a question

[mikee65]

I wish I had an inside source  ,

I think its usually +4,

Im fundamentals btw.

[mikee65]

I wrote down like 3/4 of a page + whatever diagrams I could recall from memory, Im wasnt sure exactly how much detail they wanted, ill probably get like 8/10, oh well

[mankay]

I've done this question (Q 24) about 5 times now and keep on getting (C), however, the answers says i'm wrong...

Can anybody help/tell me what they get?

[Whatlol]

isnt it just Kb = x[0.1x0.1]/[0.1x0.05] (dilution cancels out)

so x =9x10^-6

[H+] = 10^14/9x10^-6
.: ph =-log(1.11x0^-9) =8.95

[happyhappyland]

Calculated I can lose 40marks on bio, and I reckon I did. Drew two diagrams for the mentrual cycle one and hoping for like 3 marks or so out of 10. I felt the exam did not really cover the scope of the whole course as I studied a lot of other topics in depth.

Chem is easy, the questions are often in the same style and espically the organic and inorganic chem because rizza and abraham have been teaching those for yearsss

[mankay]

isnt it just Kb = x[0.1x0.1]/[0.1x0.05] (dilution cancels out)

so x =9x10^-6

[H+] = 10^14/9x10^-6
.: ph =-log(1.11x0^-9) =8.95

That makes sense accept for the start. Wouldnt what you're doing, implys that at the instant the two solutions are mixed, there are already OH- ions and there is no change from this?

---

Actually ignore the above. in the Kb expression, you're giving moles of the ions instead of the *concentrations*. That being said, your working leads to the correct answer... Anyone?

[happyhappyland]

isnt it just Kb = x[0.1x0.1]/[0.1x0.05] (dilution cancels out)

so x =9x10^-6

[H+] = 10^14/9x10^-6
.: ph =-log(1.11x0^-9) =8.95

That makes sense accept for the start. Wouldnt what you're doing, implys that at the instant the two solutions are mixed, there are already OH- ions and there is no change from this?

---

Actually ignore the above. in the Kb expression, you're giving moles of the ions instead of the *concentrations*. That being said, your working leads to the correct answer... Anyone?

I got the answer...convert to everythign to the new concentration since theres a new volumne.

WRite down Kb equation which is [OH][NH4]/ [NH3]. Put in the new concentrations of nh4 and nh3 to work out OH using KB. -log it and 14- that is the ph.

[Whatlol]

yea the volumes cancel out. You can write (0.001/0.15)/(0.005/0.15) if you want.. but it doesn't change anything

[happyhappyland]

yea the volumes cancel out. You can write (0.001/0.15)/(0.005/0.15) if you want.. but it doesn't change anything

They dont
[ NH4+ ] is 0.06666667
[ NH3 ] is 0.03333333

[mikee65]

Calculated I can lose 40marks on bio, and I reckon I did. Drew two diagrams for the mentrual cycle one and hoping for like 3 marks or so out of 10. I felt the exam did not really cover the scope of the whole course as I studied a lot of other topics in depth.

Chem is easy, the questions are often in the same style and espically the organic and inorganic chem because rizza and abraham have been teaching those for yearsss

Which specific qs do you think you messed up (if you can remember)

[Whatlol]

yea the volumes cancel out. You can write (0.001/0.15)/(0.005/0.15) if you want.. but it doesn't change anything

They dont
[ NH4+ ] is 0.06666667
[ NH3 ] is 0.03333333

... 0.0667/0.033 = (0.1x0.1)/(0.05x0.1)

[mankay]

I got the answer...convert to everythign to the new concentration since theres a new volumne.

Ohhhhhh, right. I forgot to take into account the volume change. Thanks!

[happyhappyland]

Calculated I can lose 40marks on bio, and I reckon I did. Drew two diagrams for the mentrual cycle one and hoping for like 3 marks or so out of 10. I felt the exam did not really cover the scope of the whole course as I studied a lot of other topics in depth.

Chem is easy, the questions are often in the same style and espically the organic and inorganic chem because rizza and abraham have been teaching those for yearsss

Which specific qs do you think you messed up (if you can remember)

Hair lice was hard... cellular respiration i got confused in a few of the blanks. I forgot what myosin was. Tbh i prepared alot more on development, plants and anatomy of reproduction. none of which really came up.