Destroyer Gchem #182

[osimsDDS]

An indicator is red in the undissociated form and yellow in the dissociated form. If a solution wre at a very low pH, what color would the indicator appear?

HIN ----> H+ + IN-

So I know that if you have a strong acidic solution you have a lot of H+ so it will push the equillibrium to the left (because when adding H+ the solution shifts to the left due to le chatliers princ.)

Now if you had a basic solution...would that mean that you have more HIN and then the equillibrium would shift to the right????

thanks

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[yakuza]

Actually so EQ will shift right in a basic solution and HIN will be unfavored, doesn't that mean you have less HIN?

 

[Danny289]

hey Buddy the answer is yellow? if i see this test I will go for yellow, but you know destroyer questios are tricky. if the answer is yellow I will explain it and if I am wrong, it is

 

[osimsDDS]

hey Buddy the answer is yellow? if i see this test I will go for yellow, but you know destroyer questios are tricky. if the answer is yellow I will explain it and if I am wrong, it is

No the answer is red because your in an acidic solution which makes sense you have H+ which increases the concentration of the H+ in the dissociated form and therefore moves the equillibrium to the left (undissociated form) and makes it red...

My question is tho what if its a basic solution, iam assuming it will shift to the right making it yellow (dissociated form)???

What i dont understand is that indicators are weak acids...therefore the NI- is a strong conjugate base...if you put it in a basic solution it will increase the NI- and cause it to yet again shift to the left forming red...

SOOOO SOMEONE EXPLAIN PLEASE WHAT HAPPENS!!!!

 

[Danny289]

No the answer is red because your in an acidic solution which makes sense you have H+ which increases the concentration of the H+ in the dissociated form and therefore moves the equillibrium to the left (undissociated form) and makes it red...

My question is tho what if its a basic solution, iam assuming it will shift to the right making it yellow (dissociated form)???

What i dont understand is that indicators are weak acids...therefore the NI- is a strong conjugate base...if you put it in a basic solution it will increase the NI- and cause it to yet again shift to the left forming red...

SOOOO SOMEONE EXPLAIN PLEASE WHAT HAPPENS!!!!

shoot! yes it is red I confused by the words( I meant red because indicator will be in undissociated form. listen buddy take look to destroyer organic question 101! yes don't suprise look at that question and assume that amine is indicator(cooH part).
if indicator color change in acidic solution is not meaning it is going to change in basic. the color change will be related to you condition. here it will be red because the indicator will be in undissociated form. now lets go a little bit deeper. If you add base very slowly to this solution( you decrease your acidic) the indicator will be in dissociated form and color will be changed to yellow. why?
because you come to the point the solution is more basic(or less acidic) comapre to the indicator then your indicator will be dissociatedand color will be yellow.
how about the basic solution;
answer is no, the color will not be changed because the H+ will react with base( you are not going to have H+ then no color change)
somebody correct me if I am wrong

 

[jdent]

An indicator is red in the undissociated form and yellow in the dissociated form. If a solution wre at a very low pH, what color would the indicator appear?

HIN ----> H+ + IN-

So I know that if you have a strong acidic solution you have a lot of H+ so it will push the equillibrium to the left (because when adding H+ the solution shifts to the left due to le chatliers princ.)

Now if you had a basic solution...would that mean that you have more HIN and then the equillibrium would shift to the right????

thanks

Use the derived equation (HIN)/(IN-) = (H+)/(Ka)
Looking at the two sides of the equation we see that they are proportional to each other. As H+ goes up HIN will go up. Therefore, at a low pH, hence more acidic, the H+ value increases and therefore the HIN will increase. If HIN increases then more red will be present.

 

[hdu]

In a basic environment the indicator will be dissociated and it will be yellow.

NIH <-----> NI- + H+

Add X(OH) that dissociates (OH-) + (X+)

(OH-) bind to H+ producing water

H+ is consumed, the reaction goes to the right

the (NI-) predominates

so, the solution becomes yellow in a basic environment

Note: NI- is a strong conjugate base, as are all the conjugate bases of weak acids, but (OH-) is the strongest base, so the protons will bind (OH-) and not to (NI-)

My blog www.biochemistryquestions.wordpress.com

 

[osimsDDS]

FINALLLYYYY thanks that makes a crap load of sense...thanks a lot man

 

[klutzy1987]

FINALLLYYYY thanks that makes a crap load of sense...thanks a lot man

This is just a cleverly disguised Lechatalier principle. Since the indicator is a weak organic acid in a very acidic solution it will take the undisscociated form HIn--->In- + H+ . The acidic environment will push the reaction toward the HIn form. (same idea as a commojn ion effect).
In a basic medium the H+ ions in solution will be decreased due to reaction with the OH- molecules of the base. If there is a decreased amount of H+ the reaction will shift to make more H+ and therefore more In- as well. Therefore the reaction will favor the undissociated form in a basic medium.

 

[winkipink]

what version destroyer do you guys have? I can't find this question in my destroyer. the date on my book says march 29, 2007 though... are there different versions? in gchem mine only goes up to 177 questions...