Respuesta :
Answer:
5.90g of NaClO are needed
Explanation:
Assuming the weak acid is HClO pKa = 7.54
To solve this question we must use the H-H equation for acids:
pH = pKa + log [A-] / [HA]
Where pH is the pH we want = 7.74
pKa is pKa of the weak acid = 7.54
[A-] could be taken as the moles of the conjugate base (Moles NaClO) and [HA] moles weak acid = 0.500L * (0.10mol/L) = 0.0500 moles HClO
Replacing:
7.74 = 7.54 + log [NaClO] / [0.0500 moles]
0.20 = log [NaClO] / [0.0500 moles]
1.5849 = [NaClO] / [0.0500 moles]
Moles NaClO = 0.0792 moles
The mass is: -Molar mass NaClO = 74.44g/mol-
0.0792 moles * (74.44g / 1mol) =
5.90g of NaClO are needed
5.90g of NaClO mass of the sodium salt of the conjugate base are need to make the buffer with a pH of 7.74.
What is pH?
pH tells the solution is acidic or basic. pH means potential hydrogen.
Given,
Assuming the weak acid is (hypochlorous acid) HClO
pKa = 7.54
[tex]pH = pKa + \dfrac{ log[A-] }{ [HA]}[/tex]
(Moles NaClO) and [HA] moles weak acid = 0.500L * (0.10mol/L) = 0.0500 moles HClO
Putting the value
[tex]7.74 = 7.54 + \dfrac{ log[NaClO] }{ [0.0500 moles]}\\0.20 =\dfrac{ log}{[0.0500 moles]} \\1.5849 =\dfrac{ [NaClO]}{Moles\;of\; NaClO } = 0.0792 moles[/tex]
The mass is
Molar mass NaClO
= 74.44g/mol - 0.0792 moles * (74.44g / 1mol)
=5.90g of NaClO are needed
Thus, 5.90g of NaClO are needed.
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