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gayaneshka [121]
3 years ago
10

The ka of hf is 6.8 x 10-4. what is the ph of a 0.35 m solution of hf?

Chemistry
1 answer:
damaskus [11]3 years ago
6 0
When the reaction equation is:

HF ↔ H+   +   F-

and when the Ka expression
= concentration of products/concentration of reactions

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

when we assume:

[H+] = [F-] = X

and [HF] = 0.35 - X

So, by substitution:

6.8 x 10^-4 = X^2 / (0.35 - X) by solving for X

∴ X = 0.015 M

∴[H+] = X = 0.015

when PH = -㏒[H+]

∴PH = -㏒0.015

        = 1.8
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Typical frequencies for several types of electromagnetic radiation are given below. Calculate the energy of each type of radiati
marusya05 [52]

Explanation:

The energy of electromagnetic radiation is given by :

E=h\nu

Where, h is the Planck's constant

(a) A gamma ray, \nu = 1.64\times 10^{20}\ Hz

Energy,

E=6.63\times 10^{-34}\times 1.64\times 10^{20}\\E=1.08\times 10^{-13}\ J

(b) A microwave, \nu = 4.95\times 10^{10}\ Hz

Energy,

E=6.63\times 10^{-34}\times 4.95\times 10^{10}\\E=3.28\times 10^{-23}\ J

(c) A AM radio wave, \nu = 2\times 10^{6}\ Hz

Energy,

E=6.63\times 10^{-34}\times 2\times 10^{6}\\E=1.32\times 10^{-27}\ J

Therefore, this is the required solution.

4 0
3 years ago
Muscle physiologists study the accumulation of lactic acid [ch3ch(oh)cooh] during exercise. food chemists study its occurrence i
Drupady [299]
The provided information are:
volume of 0.85 M lactic acid = 225 ml
volume of 0.68 M sodium lactate = 435 ml
Ka of the lactate buffer = 1.38 x 10⁻⁴
 The equation for dissociation of lactic acid is:
CH₃CH(OH)COOH(aq) + H₂O ⇄ CH₃CH(OH)COO⁻(aq) + H₃O⁺(aq)
The pH of buffer is calculated from Henderson-Hasselbalch equation, which is:
pH = pKa + log \frac{[conjugated base]}{[Acid]}
pKa = - log Ka = - log (1.38 x 10⁻⁴) = 3.86 
The number of moles of lactic acid and lactate are as follows:
n (Lactic acid) = 225 ml x 0.85 mmol/ml = 191.25 mmol
n (Lactate) = 435 ml x 0.68 mmol/ml = 295.8 mmol
The number of moles of lactic acid and lactate in total volume of the solution:
[CH₃CH(OH)COOH] = n (lactic acid) / 660 ml = 191.25 mmol / 660 ml = 0.29 M
[CH₃CH(OH)COO⁻] = n (lactate) / 660 ml = 0.45 M
pH = 3.86 + log \frac{0.45 M}{0.29 M} = 3.86 + 0.191 = 4.05
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7 0
3 years ago
Which of the following is NOT true regarding Rutherford's Gold Foil experiment?
erastova [34]

Answer:

The area around the nucleus must be of low mass.

Explanation:

Rutherford`s experiment showed that there are some positive charges in the center of the atoms, and because they are all together, they will give a great mass to the atom.

It was quite different from Thomson`s experiment, in which it was thought that the negative charges were mixed with the positive charges, around the atom (like a Pudding Model). In Rutherford`s experiment, because the direction of beta particles, it was the prediction of the positive nucleus.

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Which of the following would contain 48 electrons?
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The answer is cadmium its got 48 electrons which is y its number 48 on the period table
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3 years ago
7. Diethyl ether burns in air according to the following equation. C4H10O(l) + 6O2 (g) → 4CO2 (g) + 5H2O(l) If 7.15 L of CO2 is
iren [92.7K]

From the stoichiometry of the combustion reaction, we can see that 7.4 L of oxygen is consumed.

<h3>What is combustion?</h3>

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We can obtain the number of moles of CO2 from;

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n = 0.22 moles

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x moles of oxygen produces 0.22 moles of CO2

x = 0.33  moles

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0.33 moles of oxygen occupies 0.33 moles *  22.4 L/ 1 mole

= 7.4 L of oxygen

Learn more about stoichiometry: brainly.com/question/13110055

#SPJ1

6 0
2 years ago
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