Question #5e0ee
1 Answer
Explanation:
This one is pretty straightforward - you need to use an ICE table and the known value of the base dissociation constant,
So, ethylamine,
Use an ICE table to help you with the calculations
#"C"_2"H"_5"NH"_text(2(aq]) + "H"_2"O"_text((l]) -> "C"_2"H"_5"NH"_text(3(aq])^(+) " "+" " "OH"_text((aq])^(-)#
By definition, the base dissociation constant,
#K_b = (["C"_2"H"_5"NH"_3^(+)] * ["OH"^(-)])/(["C"_2"H"_5"NH"_2])#
#K_b = (x * x)/(0.075 - x) = 6.4 * 10^(-4)#
Because
#0.075 - x ~~ 0.075#
The equation becomes
#x^2/0.075 = 6.4 * 10^(-4)#
#x = sqrt(0.075 * 6.4 * 10^(-4)) = 0.006928#
The concentration of hydroxide ions will thus be
#["OH"^(-)] = x = "0.006928 M"#
To get the pH of the solution, calculate the
#"pOH" = -log(["OH"^(-)])#
#"pOH" = -log(0.006928) = 2.16#
The pH of the solution will thus be
#"pH" = 14 - "pOH"#
#"pH" = 14 - 2.16 = color(green)(11.84)#