GAMSAT sample paper Unit 9 help

spotsanddots · 28-08-2011 10:07am #1

the conversion of sucrose to fuctose and glucose in acid ic solution can be represented by the following eqn

Sucrose(aq) + H20 (H+ above arrow)-> fructose(aq) + Glucose

Rate law for rxn is rate =k(H+)(sucrose)

let the rate f the reaction at pH 3 be r .If all the variable are kept constant except that pH is changed to 2 then the rate will be ??

so does that mean

r=k(3)(Sucrose)
r/3=k(sucrose)
?? but whats the story with the ph change of 2?

imported_guy · 28-08-2011 11:47am

spotsanddots wrote: »

the conversion of sucrose to fuctose and glucose in acid ic solution can be represented by the following eqn

Sucrose(aq) + H20 (H+ above arrow)-> fructose(aq) + Glucose

Rate law for rxn is rate =k(H+)(sucrose)

let the rate f the reaction at pH 3 be r .If all the variable are kept constant except that pH is changed to 2 then the rate will be ??

so does that mean

r=k(3)(Sucrose)
r/3=k(sucrose)
?? but whats the story with the ph change of 2?

you should really be posting these in the relevant chemistry/physics forums you will get a much better response

Jammyc · 28-08-2011 12:47pm

pH 2 is ten times as acidic as pH3 and 100 times as acidic as pH4.

Seeing as the rate is dependant on the H+ concentration, a pH change from 3 to 2 would bring a 10 fold increase in the H+ conc.

Not sure what the answer would be but thats what I can see in it.

Kbear · 28-08-2011 7:44pm

pH = -log[H+]

A pH 3 = 0.001 M H+
A pH 2 = 0.01 M H+
Therefore, at a pH of 2 the concentration of hydrogen ions is 10 times greater than at a pH of 3

Answer= 10r

spotsanddots · 29-08-2011 9:27am

your right the answer is 10 times the rate 10r

GAMSAT sample paper Unit 9 help

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