A Gchem question!!Need help!

[Ocean5]

---

Members do not see this ad.

Hi every one,

There is this question in Kaplan. Chapetr 10 of G-Chem , question /Numebr 5.
It says if 10 ml of a 1 M naoh is titrated with 1M HCL to a ph of 2, what volume of hcl is neede?

I know the NV=NV rule, however. Second part which iis to ph of 2 makes it complicated and I don't understand that part. COuld you please xplain to me this question in a simple manner?
How the calculations for this kind is done? thanks

 

[Ocean5]

Hi every one,

There is this question in Kaplan. Chapetr 10 of G-Chem , question /Numebr 5.
It says if 10 ml of a 1 M naoh is titrated with 1M HCL to a ph of 2, what volume of hcl is neede?

I know the NV=NV rule, however. Second part which iis to ph of 2 makes it complicated and I don't understand that part. COuld you please xplain to me this question in a simple manner?
How the calculations for this kind is done? thanks

Obviously no one knows this?!!!!!

 

[levyusupov]

they have that question on TS and Achiever too. it is too complicated question for the DAT and probably will not be asked. dont study that qustion, just know the equations for titration, dilution, and nutralization !!!

i know the solution to that question, it is tool long and it will confuse you!!!

btw, the answer is 0.2 or 0.1 ml needed, i forgot the exact answer, but i am sure it is very low amount !!!

 

[Ocean5]

they have that question on TS and Achiever too. it is too complicated question for the DAT and probably will not be asked. dont study that qustion, just know the equations for titration, dilution, and nutralization !!!

i know the solution to that question, it is tool long and it will confuse you!!!

btw, the answer is 0.2 ml needed !!

I appreciate your help. But it has been killing me since I spent a good couple hurs to search from different sources and at the end didn't find an answer, I've been really eager to know how it is done. At least I won't regret how much I spent on that. I know that it is a trouble to write that much, but I really appreciate your help. Thank you.

 

[levyusupov]

first step:

N1V1=N2V2
(10)(1)=(1)(V2)

V2=10ml (this is the amount neede to nutrelize !!!!!)
thus, the total volume of the soultion 20ml (10 for acid and 10 for for base)
second step:

now, pH=2 means that the acid concentaration is 1x10^-2 or 0.01 (keeps this in mind)

so we do N1V1=N2V2 again, but with the new data:

N1 (NAOH)= 1N
V1= x
N2= 0.01
V2= (20+x)

ok, just plug in and solve for x and you will get 0.2ml, which is the amount needed !!!!!!!

who's the man !!!!!

 

[Ocean5]

first step:

N1V1=N2V2
(10)(1)=(1)(V2)

V2=10ml (this is the amount neede to nutrelize !!!!!)
thus, the total volume of the soultion 20ml (10 for acid and 10 for for base)
second step:

now, pH=2 means that the acid concentaration is 1x10^-2 or 0.01 (keeps this in mind)

so we do N1V1=N2V2 again, but with the new data:

N1 (NAOH)= 1N
V1= x
N2= 0.01
V2= (20+x)

ok, just plug in and solve for x and you will get 0.2ml, which is the amount needed !!!!!!!

who's the man !!!!!

YOU ARE!!😛 Now the thing is that there are a couple different ways to solve the second section, right? I don't know why x in 20 + x is negligible.
Another thing is that we can solve this second part just using X> 2, but I don't know that why we can, is that b/c it is a dilute soln in second part? Is it a dilute soln in the second part (to start)?

 

[levyusupov]

nothing is negligible in this problem,

that is how you set this up :

(1)(x)=(0.01)(20+x)

dont neglaect anything, just unfold and solve for x !!!!

can you explain yourself for your second question? i dont understand what you trying to ask.

 

[Ocean5]

nothing is negligible in this problem,

that is how you set this up :

(1)(x)=(0.01)(20+x)

dont neglaect anything, just unfold and solve for x !!!!

can you explain yourself for your second question? i dont understand what you trying to ask.

I didn't get that where (20 + x ) is coming from. sorry to post little late. I've been trying to figure it out for about 5 mins now. Where that x in (20 + x ) is coming from. Yes, I undertsand that our total soln is 20 ml now. but what is that x?

 

[levyusupov]

the x in the x+20 is the amount of ACID needed to to added to the nuetrelized solution in order to have a pH=2 !!!

think about it, you need more acid to push it towards the acidic.

i know from first glance it looks a little amount but if u look at titration curve of strong base vs strong acid you will see the quick turning point and the quick falling of the line upon addition of small amount of acid

 

[Ocean5]

the x in the x+20 is the amount of ACID needed to to added to the nuetrelized solution in order to have a pH=2 !!!

think about it, you need more acid to push it towards the acidic.

i know from first glance it looks a little amount but if u look at titration curve of strong base vs strong acid you will see the quick turning point and the quick falling of the line upon addition of small amount of acid

I just read your last post. Yes it does make sense. thanks alot. It is 1:03 and I have to get some sleep. Thanks again. See you tomorrow. By the way, when is your DAT?

 

[levyusupov]

I just read your last post. Yes it does make sense. thanks alot. It is 1:03 and I have to get some sleep. Thanks again. See you tomorrow. By the way, when is your DAT?

if i will tell you my date i will have to hunt u and kill you 😉😉🙂🙂

 

[levyusupov]

just kidding, dont get scared !!

my DAT is on 09/04/2007.