Kb=1.3X10^-3
2007-02-01 14:35:55 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Kb = [(C2H5)2NH2+][OH-]/[(C2H5)2NH]
As diethylamine dissolves, a certain portion x will react with water, which doesn't show up in the Kb expression, to form diethylammonium ion and hydroxide. Thus, the diethylammonium concentration will be x, as will the hydroxide concentration, and diethylamine will be 0.05-x.
So, the equation will be:
1.3 x 10^-3 = x^2/(0.05-x)
Since 1.3 x 10^-3 is not much smaller than 0.05, x will not be insignificant compared to 0.05, so you cannot drop the x from the expression in the denominator. Rearrange the equation to get it into the form of ax2 + bx + c = 0 and use the quadratic to solve.
x^2 + (1.3 x 10^-3)x - 6.5 x 10^-5 = 0
Once you get x, take the -log of that number to get pOH, then subtract that number from 14 to get pH.
2007-02-01 14:52:47 · answer #1 · answered by TheOnlyBeldin 7 · 0⤊ 0⤋
Diethylamine Ph
2016-12-11 15:16:40 · answer #2 · answered by dymke 4 · 0⤊ 1⤋
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The equation for finding pH is pH = -log [H3O+] the concentration of H3O+ is given as 1.4 x 10^-2 so pH= -log (1.4 X10^-2)= -log (.014) = -(-1.85) =1.85 ( the concn is .014 not 1.4) You can also be asked to find OH- concentration which is calculated as [OH-] = 1X 10-14/ [H3O+]
2016-04-09 06:02:42 · answer #3 · answered by Anonymous · 0⤊ 0⤋