Posted by Anonymous on Thursday, November 4, 2010 at 10:32am.
Ka=[H][COOH]/([HCOOH]
ka= x^2/(.5-x)
solve this for x
x^2+.00018x-.5*.00018=0
x=(-.00018+-sqrt(.00018^2+.00036))/2
x=-.00009+- .00948= .00939 check all that math.
pH=-log (.00939)=2.03
check the math.
The equilibrium is given by
HCOOH -> H+ + HCOO-
so Ka=[H+][HCOO-]/[HCOOH]
if we start with 0.5M HCOOH then at equilibrium there is [H+] = x and [HCOO-]=x and HCOOH=0.5-x
so Ka = (x)(x)/(0.5-x)=0.00018
this gives a quadratic to solve, however, we only want the answer to 1 sig fig (.5M is 1 sig fig) so we can say that 0.5-x is approximately equal to 0.5, because x will be small.
thus x^2/0.5=0.00018
hence you can find x
pH is then -log(x)
which is pH=2, but check the maths.
Related Questions
Chemistry - Calculate the pH of solution made by combining 75.0 mL of 0.10 M ...
chemistry - A. Strong Base 1.) What is the concentration of a solution of KOH ...
AP Chemistry - A buffer solution contains .4mol of formic acid, HCOOH and a ....
Chemistry - Find the pH of mixture of acids. 0.185 M in HCHO2 and 0.225 M in ...
CHEM - Calculate the pH of solution made by combining 75.0 mL of 0.10 M formic ...
Chemistry - How many grams of formic acid, HCOOH, must be added to 0.270L of 0....
Chemistry - A 50.0 mL sample of 0.12 M formic acid, HCOOH, a weak monoprotic ...
Chemistry - calculate the pH at 0ml at the quivalence point and at 40ml in a ...
chemistry - What is the original molarity of a solution of formic acid (HCOOH) ...
chem ll - How many grams of formic acid, HCOOH, must be added to 0.270L of 0....
For Further Reading
