URGENT !! A substance has 55.80% carbon, 7.04% Hydrogen, and 37.16% Oxygen. What is it's empirical and molecular formula if it h
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Answer:
A mixture of 100. mL of 0.1 M HC3H5O3 and 50. mL of NaOH
Explanation:
The pH of a buffer solution is calculated using following relation
Thus the pH of buffer solution will be near to the pKa of the acid used in making the buffer solution.
The pKa value of HC₃H₅O₃ acid is more closer to required pH = 4 than CH₃NH₃⁺ acid.
pKa = -log [Ka]
For HC₃H₅O₃
pKa = 3.1
For CH₃NH₃⁺
pKa = 10.64
pKb = 14-10.64 = 3.36 [Thus the pKb of this acid is also near to required pH value)
A mixture of 100. mL of 0.1 M HC3H5O3 and 50. mL of NaOH
Half of the acid will get neutralized by the given base and thus will result in equal concentration of both the weak acid and the salt making the pH just equal to the pKa value.
According to Hasselbach-Henderson equation:
Here, is concentration of conjugate base and [HA] is concentration of acid.
In the given problem, conjugate base is and acid is
thus, Hasselbach-Henderson equation will be as follows:
...... (1)
(a) Ratio of concentration of potassium acetate and acetic acid is 2:1 thus,
Also,
Putting the values in equation (1),
Therefore, pH of solution is 5.06.
(b) Ratio of concentration of potassium acetate and acetic acid is 1:3 thus,
Also,
Putting the values in equation (1),
Therefore, pH of solution is 4.28.
(c)Ratio of concentration of potassium acetate and acetic acid is 5:1 thus,
Also,
Putting the values in equation (1),
Therefore, pH of solution is 5.45.
(d) Ratio of concentration of potassium acetate and acetic acid is 1:1 thus,
Also,
Putting the values in equation (1),
Therefore, pH of solution is 4.76.
(e) Ratio of concentration of potassium acetate and acetic acid is 1:10 thus,
Also,
Putting the values in equation (1),
Therefore, pH of solution is 3.76.