I keep getting wrong answers for this question.
Determine the pH of an HF solution of each of the following concentrations.
a) .280 M
b) 5.3*10^-2 M
c) 2.50*10^-2 M

No Ka has been given. I haven't attempted b or c yet because I want to at least solve a first. So far I got a answer of 3.75 and 1.88 and both are incorrect. I think I know how to solve for this. Using Ka and approximations. I just don't understand where I am going wrong. Thanks in advance!

  1. 👍
  2. 👎
  3. 👁
  1. These can't be solved with a Ka value. Why don't you post your work for a and let me look at it. I'm sure I'll see immediately what is going on.

    1. 👍
    2. 👎
  2. Oh okay I thought you used Ka to solve these. That's what I'm doing wrong. I tried looking up the Ka for HF and multiplying it to .280 then take the -log of that number. The reason why I had to different numbers is because I found two different Ka's. If I can't use Ka do I just take the -log of .280?

    1. 👍
    2. 👎
  3. First I made a typo with my response. You certainly DO need Ka and that's the only way you can do it. I just didn't type in with instead of without.
    My text hqas 7.2E-4 for HF.
    ...........HF ==> H^+ + F^-

    Ka = 7.2E-4 = (x)(x)/(0.280-x)
    Solve for x and convert to pH.
    Probably you can get by without a quadratic equation for the 0.280but it may take one for the others, especially the very weak one.
    Using this value I get 1.85 for the pH of the 0.280 M soln. Your text may give a different value for Ka.

    1. 👍
    2. 👎
  4. the pH is NOT 1.85

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. chemistry

    2C2H2(g) + 5O2(g)→4CO2(g) + 2H2O(g) a. Determine the enthalpy change for the reaction. ΔH = (4(-393.5)+ 2(-241.8)) – (2(227) + 5(0)) The enthalpy change is -2511.6. b. Determine the entropy change for the reaction. ΔS =

  2. Statistics

    A 10 question test is all multiple choice. Each question has four choices. Determine the mean number of questions answered correctly as well as the standard deviation for the number of correct answers if someone were to guess on

  3. Differential Equations

    Find the general solution of the given differential equation. x dy/dx − y = x^2 sin x I have solved to: y = -x cos(x) + cx The second part of the question is to give the largest interval over which the general solution is

  4. Algebra

    Determine the value or values of d that complete the square for the expression. (Enter your answers as a comma-separated list. If there is no solution, enter NO SOLUTION.) (a) x^2 + 7x + d d = b) x^2 − 18x + d d = (c) x^2 + dx +

  1. Statistics

    There are 3 short questions on math test. for each question, 1 mark will be awarded for a correct answer and no mark for wrong answer. if the probability that mary correctly answers a question in a test is 2/3, determine the

  2. Alg 1

    Completing the square: Which of the following is a solution x^2 + 14x + 112 = 0? If necessary round to the nearest hundredth. x= -0.24 x= -4.24 x= 4.24 no solution I worked it and got neither of the answers. I got x= 0.9 and

  3. chemistry

    A radio station's channel, such as 100.7 FM or 92.3 FM, is actually its frequency in megahertz (MHz), where 1 MHz =10^6 Hz}. Calculate the broadcast wavelength of the radio station 98.70 FM. can someone please explain this

  4. physics

    vector (V1) is 6.3 units long and points along the negative (X) axis. Vector(V2) is 9.0 units long and points at 55 degree to the positive (X)axis. 1- What are the (X) and (Y) components of (V1) vector ? 2-What are the (X) and (Y)

  1. PreCalc

    Approximate the solutions to the following equation on the interval [0,2π). Round your answer to four decimal places. sinθ=0.65 Apparently, there suppose to be two answers to this question with a comma separating​ both

  2. statistics

    quiz consists of 7 multiple choice questions. each question has 5 answers, one of which is correct. if random guess is made, find the probability that 3 answers will be correct and 4 wrong

  3. Chemistry

    Hydroxyapatite, Ca10(PO4)6(OH)2Ca10(PO4)6(OH)2 , has a solubility constant of Ksp = 2.34×10−592.34×10−59 , and dissociates according to Ca10(PO4)6(OH)2(s) --> 10Ca2+(aq) + 6PO4^3-(aq) + 2OH-(aq) Solid hydroxyapatite is

  4. Math

    Please Check My Answer I don't know if they are right or wrong and if they are wrong can u give me the correct answers. ? Thanks PS: The answers are the * one's. 1) 2/3 = 12/x x= 18 x= 12 x= 36 x= 8 **************** 2) 6/11 = 84/x

You can view more similar questions or ask a new question.