CSSA Chemistry (2 Viewers)

[Dylanamali]

the answer is C

great! do you understand? if not I can try to explain better. I didn't mention how this resulted in an increased concentration of the chromate ion, but assumed you knew how Le Chantelier's principle worked.

 

[Dylanamali]

lol ur preey good, r u sitting ur test 2moz

yeah tommorow CSSA paper, slightly worried, but hopefully everything will click =). I think all the knowledge based questions are okay, the calculations can sometimes get difficult with CSSA papers.

 

[adz1098]

Yeah Ive like 4 years of cssa papers, there alot harder than hsc.

 

[adz1098]

Equal volumes of four 0.1 mol L−1 acids were titrated with the same sodium hydroxide
solution.
Which one requires the greatest volume of base to change the colour of the indicator?
(A) Citric acid
(B) Acetic acid
(C) Sulfuric acid
(D) Hydrochloric acid

I sit A because its triprotic?

 

[Dylanamali]

Equal volumes of four 0.1 mol L−1 acids were titrated with the same sodium hydroxide
solution.
Which one requires the greatest volume of base to change the colour of the indicator?
(A) Citric acid
(B) Acetic acid
(C) Sulfuric acid
(D) Hydrochloric acid

Yes that is the perfectly correct reasoning. In titration it is all about getting the no. of moles of H+ equal to that of OH- (eq. point). Citric acid is triprotic and will thus need 3 times the amount of mols of NaOH.

I sit A because its triprotic?

 

[iAmCurium96]

wont it be D? HCL is the strongest out of the 4

 

[adz1098]

cool

 

[Dylanamali]

wont it be D? HCL is the strongest out of the 4

Yeah initially I thought that awhile ago.. however because the equivalence point is only dependent on the molar ratio this is not the case. Because you will need three times as many moles of NaOH to neutralise citric acid (triprotic) acid then you will to neutralise HCl - because of this you need more volume of NaOH to neutralise citric acid. You even need more to neutralise sulfuric acid which is diprotic. And even then, it is difficult to say which is stronger between HCl and H2SO4 they are both very strong.

 

[chels777]

H2SO4 is stronger than HCL as it is diprotic im pretty sure the answer would be c because citric acid is in equilibrium and is a weak acid therefore there is not as many H+ ions within the same amount of solution

 

[hscishard]

yea C. H2SO4 is strong, the HS04 is weak, but it still gives off more hydronium ions
Though I think citric, depending on it's position of equilibrium could over take h2so4

 

[silence--]

the answer is A (citric), because of its triprotic nature. In this case the degree of ionisation doesn't matter because the question tells you that they have equal concentrations (and equal volumes). If you write equations for all the reactions and plug in arbitrary numbers (V=n/c) you can confirm.

btw question was from 2010 hsc (iirc)

 

[Banana-Hammock]

That's what happens when girls try to do MX1.

excuse me i rule MX1

 

[Riproot]

excuse me i rule MX1

Shhhhhh, Princess Consuela Banana-Hammock.