Chemistry with buffers?

A beaker with 100 ml of an acetic acid buffer with a pH of 5.00 is sitting on a benchtop. The total molarity of acid and conjugate base in this buffer is 0.100 M. A student adds 7.30 ml of a 0.360 M HCl solution to the beaker. How much will the pH change? The pKa of acetic acid is 4.760.Chemistry with buffers?
pH = pKa + log (base/acid)



5.00 = 4.76 = log (x/1)



I want the ratio of base to acid which is why I used x/1



log x = 0.24



x = 1.74



my base:salt ratio is 1.74:1



let x = moles of acid



1.74x + x = 0.01 total moles of solute



x = 0.00365 moles (this is the acid)

base = 0.00635 mol



Add strong acid, it protonates the base



(0.360 mol/L) (0.00730 L) = 0.002628 mol of strong acid added



base: 0.00635 - 0.002628 = 0.003722

acid: 0.00365 + 0.002628 = 0.006278



pH = 4.76 + log(0.003722/0.006278)



pH = 4.53



Note: I used moles in that last H-H expression rather than using the new volume of 107.3 mL to get molarities. Since there would be a 0.1073 L in the numerator and the denominator, I just skipped that step.



Good problem. Check my math carefully and talk the solution through with your study group. Best wishes.



Update:



http://www.chemteam.info/AcidBase/Hender



problem #7

Chemistry help please?

A beaker with 175 mL of an acetic acid buffer with a pH of 5.00 is sitting on a benchtop. The total molarity of acid and conjugate base in this buffer is 0.100 M . A student adds 6.90 mL of a 0.340 M HCL solution to the beaker. How much will the pH change? The pKa of acetic acid is 4.760Chemistry help please?
let x = [acetic acid]

let y = [acetate]



5.00 = 4.760 + log y/x

10^0.24 = y/x

1.74 = y/x

1.74 x = y



but we know that x + y = 0.100

y = 0.100-x

1.74 x = 0.100-x

2.74 x = 0.100

x = 0.0365 and y = 0.0635 M



moles acetic acid = 0.0365 x 0.175 L=0.00639

moles acetate = 0.0635 x 0.175 L=0.0111



moles H+ added = 6.90 x 10^-3 L x 0.340 M=0.00235

the reaction that occur is

CH3COO- + H+ = CH3COOH

moles acetate = 0.0111 - 0.00235 =0.00875

moles acetic acid = 0.00639 + 0.00235 =0.00874

total volume = 6.90 + 175 = 181.9 mL =%26gt; 0.1819 L

[acetic acid ] = 0.00874 / 0.1819 =0.0480 M

[acetate] = 0.00875/0.1819 =0.0481 M



pH = 4.760 + log 0.0481 / 0.0480=4.76

Chemistry Acid Base Buffer?

A beaker with 155 mL of an acetic acid buffer with a pH of 5.00 is sitting on a benchtop. The total molarity of acid and conjugate base in this buffer is 0.100 M. A student adds 7.60 mL of a 0.260 M HCl solution to the beaker. How much will the pH change? The pKa of acetic acid is 4.760.Chemistry Acid Base Buffer?
let x = [acetate]

let y = [acetic acid]



x + y = 0.100



5.00 = 4.760 + log x/y



5.00 - 4.760= log x/y



10^ 0.24 =1.74 = x/y



1.74 y = x



1.74 y + y = 0.100

2.74 y = 0.100

y=0.0365 M

x = 0.100 - 0.0365=0.0635 M



moles acetate = 0.0635 x 0.155 L=0.00984

moles acetic acid = 0.0365 x 0.155=0.00566



moles H+ added = 7.60 x 10^-3 L x 0.260=0.00198



CH3COO- + H+ = CH3COOH

moles acetate = 0.00984 - 0.00198=0.00786

moles acetic acid = 0.00566 + 0.00198=0.00764



total volume = 0.1626 L

[acetate]= 0.00786/ 0.1626=0.0483

[acetic acid]= 0.00764/ 0.1626=0.0470 M



pH = 4.760 + log 0.0483/ 0.0470=4.77



delta pH = 0.23

Do you think it's safe to put flagstone in a goldfish tank?

Hi,

i was wondering if it's safe to put it and build it. its a 20 gallon goldfish aquarium! a few question!

is it safe for the goldfish?

will it put to much pressure on the glass? (it's about 70 pounds)

how do i clean it fist

and will it change the PH?

is it safe for goldfish????!?!?Do you think it's safe to put flagstone in a goldfish tank?
Should be fine. Just be careful with the weight. Seventy pounds is a bit too much for a twenty gallon tank, just be sure not to put any ';points'; directly on the glass which would create a pressure crack. If you're laying it flat, no problem. I'd go with small/medium pieces, around six-eight inches, and stack them mabey halfway up the tank. A few could reach the surface. Leave the front half of the tank empty. This shouldn't be too much weight. Glass is stronger than most people think. If you have bubble-eye goldfish, be sure there are no sharp edges that could burst their bubbles! Just rinse it off in warm water to remove the dust.Do you think it's safe to put flagstone in a goldfish tank?
Why on earth would you want to do that?

Challenging Pure chemistry?

When volume of acid was added to an alkali, how does pH change during the acid -base titration?



Thank you very much for your help.Challenging Pure chemistry?
';The pH will level off';??? I don't believe that Rhiz has ever done a titration. There is no ';leveling off'; at the equivalence point. Take a look at the graph of pH vs volume of added base for the titration of an acid.

http://library.tedankara.k12.tr/chemistr

or this one for the titration of a base by an acid:

http://www.chem.ubc.ca/courseware/pH/sec



Challenging Pure chemistry?
The pH will decrease progressively...



Should this be a strong acid-strong base titration, the pH will decrease progressively then rising or descending sharply (equivalence point) along pH 7...



In a strong acid-weak base titration... the drastic descent or equivalence point will be below pH 7...
It Depends On the Buffering Capacity.
There is a non-linear response. pH changes relatively rapidly until you reach a buffering point (not really a point), a narrow pH range where the dominant compound undergoes an ion change by the addition of H+ to the base form. the pH where this occurs depends on the stability relations between the H-base and H-free base ions. You see only a slight pH change in the immediate vicinity of this point because the H+ that is added is essentially immediately combined with the base ion. after you have converted essentially all of the base to the H-base, the pH will again change rapidly.

Advice needed for sick drawf (freshwater) puffers.?

African (Malawi) cichlid tank. 75 gallons, established. PH 7.5-8.0. Chichlid salt used. No plants, only rockscape. Bought 6 puffers ~8 weeks ago. Feed mosquito larvae, brine shrimp, krill. I feed them once a day. Occasionally skip a day. Also pellet, flake, cichlid food. The puffers don't seem to eat these. No signs of illness. No problems with other fish in the tank. Found three of the puffers dead, two days ago. One is now sick. THe other two lay on the bottom but seem to have revived and are swimming around None of them have looked sick- no ich, fungus, etc. Help. I really like these guys and am not sure what to do. Is the Ph too high for them? Not enough or too muh salt? No cover? Wrong food? looked them up on the net but cannot find the answers to these questions. I have a community tank and a guppy tank I could move them to if the ph is an issue (they are 7.0)- but if so, how do you do it without shocking them by the ph change? Any suggestions would be appreciated.Advice needed for sick drawf (freshwater) puffers.?
dwarf puffers could be taking each other out -- they aren't very social and are better with heavy plants if kept in groups. from my understanding they are salt sensitive anything over a teaspoon and 1/2 in 10 gallons would be a problem.Advice needed for sick drawf (freshwater) puffers.?
Puffers should have absolutely no salt content. They are also solitary fish and would have double the stress in this big, stocked tank.
kill it. If you touch it then u will grow a fin and ure legs will be gone and then u will have a huge head and then u will eat something and it will mutate inside of u and you will become a fish!!!!!!!!!!!!!!

































jking. YA just no salt 4 him.

Decorating the bedroom need some ideas

slightest effect

Chemistry help please?

A beaker with 175 ml of an acetic acid buffer with a pH of 5.00 is sitting on a benchtop. The total molarity of acid and conjugate base in this buffer is 0.100M . A student adds 6.90 mL of a 0.340 M HCL solution to the beaker. How much will the pH change? The pKa of acetic acid is 4.760.



Basically whats delta pH?Chemistry help please?
let y = [acetate]

let x = [acetic acid]



5.00 = 4.760 + log y/x

10^0.24 = 1.74 = y/x

1.74 x = y

but we know that y + x =0.100



1.74 x = 0.100-x

x = 0.0365 M

y = 0.0635 M

moles acetic acid = 0.0365 x 0.175 L= 0.00639

moles acetate = 0.0635 x 0.175 L= 0.0111

moles H+ added = 6.90 x 10^-3 L x 0.340 M= 0.00235

CH3COO- + H+ = CH3COOH

moles acetate = 0.0111 - 0.00235 = 0.00875

moles acetic acid = 0.00639 + 0.00235 = 0.00874

pH = 4.760 + log 0.00875 / 0.00874 = 4.76



delta pH = 5.00 - 4.76=0.24