Killed by multiple choice? (2 Viewers)

[ixswans]

Looks like I made quite a few 'educated' guesses that came out right.

 

[mupy]

yeh i agree with pH --> floc --> settling --> pH (later)
i put pH adjustment AFTER floc & settling
but i didn't realise that chlorination was there in step 5. i think that was the real keyword in the question that meant you had to put pH before floc & settling.
let's hope they accept both answers!

 

[mR sinister]

Yep this was a really screwed up multiple choice...
And what did every1 get for question 14,
i done the calculation and got A, but thats not what most ppl got....

Also Question 8 would be B would it not?
CO3^2- makes a percipitate with pb^2+
But most ppl got A.. hmm

 

[David.Lai]

Yep this was a really screwed up multiple choice...
And what did every1 get for question 14,
i done the calculation and got A, but thats not what most ppl got....

Also Question 8 would be B would it not?
CO3^2- makes a percipitate with pb^2+
But most ppl got A.. hmm

it is A, because it has iodine, sure it could be B, except it said "UNAMBIGUOUSLY identify" and carbonate ions also precipitates with calcium (i.e limestone) and sodium (i.e sodium carbonate as seen in the solvay process).

in relation to the pH question, by added lime to the water, this chemical additive is part of the flocculation step, hence it is not a step by it self. Thus D is the right answer as pH adjustment is a completely different process which occurs after chlorination.

 

[TechnIx]

Fuck, i swear the MC this year was hard than previous...i no ive definitely got 3 wrong atm, the bloody Barium flame colourtest...i crossed out green immediately LOL thought copper made green...-.-",

I did the EXACT same thing. lol silly us

 

[carlytse621]

I just found a conquering chem exercise sheet and it has a diagram of water treatment
It said pH adjustment is at the end