Question

If a solution of HF (Ka = 6.8 x 10-4) has a pH of 3.65, calculate the initial concentration of hydrofluoric acid.

Answer #1

use:

pH = -log [H+]

3.65 = -log [H+]

[H+] = 2.239*10^-4 M

HF dissociates as:

HF
-----> H+ + F-

c
0 0

c-x
x x

Ka = [H+][F-]/[HF]

Ka = x*x/(c-x)

6.8*10^-4 = 2.239*10^-4*2.239*10^-4/(c-2.239*10^-4)

c-2.239*10^-4 = 7.37*10^-5

c=2.976*10^-4 M

Answer: 3.0*10^-4 M

1(A)What is the pH of a 0.448 M solution of HF with ka =
6.8*10-4?
(B)In part A you probably made the approximation that 0.448 - x
0.448. Check the approximation by calculating the % that x is of
0.448.
2)a)Calculate the molar concentration of OH− ions in an 1.71 M
solution of hypobromite ion (BrO−; Kb = 4.0 10-6).
b)What is the pH of this solution?

a. Calculate the pH of a 0.538 M aqueous
solution of hydrofluoric acid
(HF, Ka =
7.2×10-4).
b. Calculate the pH of a 0.0242 M aqueous
solution of nitrous acid
(HNO2, Ka =
4.5×10-4).

The acid disassociation constant, Ka, for hydrofluoric acid is
6.8 x 10−4. Given a 0.020 M solution of hydrofluoric acid, answer
the following questions. HF(aq) H+(aq) + F−(aq)
A. Write the equilibrium expression.
B. What is the concentration of acid, H+, in the equilibrium
solution?

A solution is made that is 0.015 M HCI and 0.10 M HF (Ka= 6.8 x
10^-4). What is the concentration of the undissociated weak acid in
the mixture?
? M

Determine the pH of a 0.200 M solution of hydrofluoric acid (HF)
(Ka = 6.3 x 10^-4)
a. 4.20
b. 3.90
c. 2.02
d. 0.69
*please show process*

What is the pH of an aqueous 0.036 M NaF
solution? Ka(HF) = 6.8 x10-4

Calculate pH of 0.10 M hydrochloric acid (why no Ka?)
Calculate the pH of a 0.100 M calcium hydroxide (hint: write the
formula first & rxn in water)
Calculate the pH and % ionization of a 0.05 M hydrofluoric acid
(ka = 8.0 x 10 -4) .
What is the hydrogen ion concentration for a hydrochloric acid
solution that has a pH of 2.30?

Calculate the pH of a 3.66×10-3 M solution of NaF, given that
the Ka of HF = 6.80 x 10-4 at 25°C.

What is the pH of a 0.010 M solution of HF? (The Ka value for HF
is 6.8×10−4.) What is the of a 0.010 solution of ? (The value for
is .)
a. 1.58
b. 2.10
c.2.30
d. 2.58
e. 2.64

A.) Find the pH of a 0.338 M NaF solution. (The Ka of
hydrofluoric acid, HF, is 3.5×10?4.)
B.) Determine the [OH?] of a 0.30 M solution of NaHCO3. and
Determine the pH of this solution.
C.)Find the [OH?] of a 0.46 M methylamine
(CH3NH2) solution. (The value of Kb for methylamine
(CH3NH2) is 4.4×10?4.) include units
D.) Find the pH of a 0.46? M methylamine
(CH3NH2) solution.

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