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D-2
A correction must be made, if the height of the column of water (h) in the buret, after reaction, is different
from the level of water in the beaker. Consider Figure 2.
The atmospheric pressure (P
atm
) pushes down on the water in the beaker and forces water up into the buret.
This external pressure is balanced by the pressure of the N
2(g)
in the buret (P
N2
), the pressure of water vapor
in the buret (P
H2O
), and the pressure exerted by the column of water in the buret above the level of the water
in the beaker (P
wc
). This balance can be expressed as:
F
ig
ure 1
Tap w
ater
S
topcock
M
eniscus
Sulfam
ic
Aci
d
Glass V
ial
containing N
aN
O2
U
-Tube
250 m
L
Erlenmeyer
Flask
400 mL
B
eaker
B
uret
Clam
p
Tubing
Rubber
S
topper
P
a
tm
h
wc
F
ig
ure 2
P
gas
+
P
H
O
2
