Question

A buffer is created by combining 140.0 ml of 0.25M HCHO2 with 75.0 ml of 0.20M NaOH .Determine the of the buffer.

Answer 1

*determine the PH

Answer 2

ok then..?

Answer 3

u knw how to calculate pH by concentration?

Answer 4

is that PH =- log [H30+]..?

Answer 5

nah i m ot able to take log (24x 10^-1)
i get this by
N1V1 +N2V2 = NV
N normality
V volume
140x0.25 + 0.20x75=N215
35+15=215V
50/215=N
0.23 ssmthing is coming

Answer 6

i m gettin pH=1.38

Answer 7

a minute

Answer 8

it's wrong..=(

Answer 9

a by rounding i take N=24 x 10^-1
pH=log(24 x 10^-1)
=log(6x4x10^-1)
=log6 + log 4 + log 10^-1
=0.78+0.60 + 1-log 10
=1.38 + 0

Answer 10

hmm.. i got this but (:

Answer 11

are u really sure..? sorry but this is my last attempt..on9 quiz..=(

Answer 12

saorry i m gettin last try ans is 1.0458 this is the final ans

Answer 13

can u tell me the options?

Answer 14

its no option..=(

Answer 15

1.05 final try this one

Answer 16

can u give me the link og quiz if u dont mind

Answer 17

in need to login..

Answer 18

*it

Answer 19

nah i was jut aking gime me the site name if u remeber

Answer 20

mylabsplus..=)

Answer 21

heena..if u dont mind, how to clculate pH of N2H4 when concentration is 0.25M?

Answer 22

simple N2H4 there the charge is 1 so to caluclate normality first so multiply concentration given in molarity with charge
now
pH=log concentration
pH=log (25 x 10^-2)
pH=2 - log 25
pH=2-log(5x5)
pH=2-log5 +log 5
= 2-0.7+0.7
=2-1.4
=0.6

Answer 23

alway remeber before taking normality always mulitply molarity x charge like in H2SO4 charge is 2 so now concentration change ok

Answer 24

normality = pH?

Answer 25

how to know the charge??

Answer 26

sorry but it says that N2H4 is a weak base..

Answer 27

pOH=log concentration
pOH=log (25 x 10^-2)
pOH=2 - log 25
pOH=2-log(5x5)
pOH=2-log5 +log 5
= 2-0.7+0.7
=2-1.4
pOH=0.6
now we know pH-pOH=14

Answer 28

sry wat hapening me i dunno u r right N2H4 is base so we will get pOH now by completing above que u ll get pH

Answer 29

You start with a "large" amount of weak acid (formic acid, HCHO2), and add to it a small amount of strong base (NaOH) which will neutralize SOME of the weak acid into the formate ion (CHO2^-1). You have to find the moles of base added, which will tell you the moles of formate ion formed. From that, find the moles of acid that were used, and the moles of acid that are left over. Turn those moles into concentrations, and use the equation that determines the pH of a buffer: \[pH = pK_{A} * \log(\frac{[Base]}{[Acid]})\]

Answer 30

but here u are not given pka

Answer 31

look up the KA of formic acid

Answer 32

i think i m lacking smwhere if u dont mind can u post the formula how to calculate KA

Answer 33

The pKa of formic acid is 1.8 x 10–4.
Now apply Henderson's equation,
pH=pKa+log(salt/acid)
salt=meq of base
acid=meq of acid-meq of base.