To the nearest hundredths, what is the pH at the end of an enzyme-catalyzed reaction if it were carried out in a 0.1 M buffer initially at pH 2.07, and 0.005 M of acid (H+) was produced during the reaction? (The buffer used was a polyprotic acid of the general form: H3A; the three pKas of this polyprotic acid are 2.07, 6.56, and 11.22.) (The enzyme's normal environment is the stomach.)
ans)
from above data that
Buffer maintain the PH of acids and bases.
PH = PKa of acids.
Here PH of 2.07 is equal to PKa =2.07
We know that formula
PH = PKa+ Log [A-]/ [HA]
2.07 =2.07 + log [A-]/ [HA]
log [A-]/ [HA] =0
Here we get
[A-]/ [HA] =0
[A-] = 0, [HA] =0
Here given concentration of phosphate buffer is 0.1M
HA + A- =0.1M
HA = 0.1M, A- = 0.1M
0.005M of acid is added to the reaction.It will reacts A- yields HA.
[A-] = 0.1-0.005 = 0.095M
[HA] = 0.1 + 0.005 = 0.105M
PH = PKa+ Log [A-]/ [HA]
= 2.07 + log [0.095]/[0.105]
= 2.07 -0.04346
=2.026
PH =2.03
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