The
reaction is<span>
C</span>₂H₄ +
O₂ → CO₂ + H₂O<span>
To balance the equation, both side have same
number of elements. Here,</span>
In left hand
side has
in right hand side has
4 H atoms
2 H
atoms
2 C atoms 1 C
atom
<span>
2 O atoms 3 O
atoms
First, we have to balance number of C atoms and number of H atoms in both side.
To balance C atoms, '2' should be added before CO</span>₂ and to balance H atoms, '2' should be added
before H₂<span>O.
Then number of oxygen atoms is </span>2 x 2 + 2 = 6 in right hand side. So, 3 should be
added before O₂<span> in left hand side.
After balancing the equation should be,</span>
C₂H₄<span> + 3O</span>₂<span> → 2CO</span>₂<span> + 2H</span>₂O
When the Pka for formic acid = 3.77
and Pka = -㏒ Ka
3.77 = -㏒ Ka
∴Ka = 1.7x10^-4
when Ka = [H+][HCOO-}/[HCOOH]
when we have Ka = 1.7x10^-4 &[HCOOH] = 0.21 m
so by substitution: by using ICE table value
1.7x10^-4 = X*X / (0.21-X)
(1.7x10^-4)*(0.21-X) = X^2 by solving this equation for X
∴X = 0.0059
∴[H+] = 0.0059
∴PH= -㏒ [H+]
= -㏒ 0.0059
= 2.23
The answer is 18 you multiply wavelength (6) times frequency (3)
