Which solutions below would be described as a buffer solution?
A) 500 mL of 0.1 M HCl added to 500 mL of 0.1 M NaOH
B) 500 mL of 0.1 M HCl added to 500 mL of 0.1 M NaCl
C) 500 mL of 0.1 M HCNO added to 500 mL of 0.1 M KCNO
D) 500 mL of 0.1 M HCNO added to 250 mL of 0.1 M KCNO
E) 500 mL of 0.1 M HCNO added to 250 mL of 0.1 M NaOH
F) 500 mL of 0.1 M HCNO added to 500 mL of 0.1 M NaOH
2. Determine the pH of the solution in question 1E given the Ka(HCNO) = 2 ´ 10‒4.
1) answers are
C) 500 mL of 0.1 M HCNO added to 500 mL of 0.1 M KCNO
D) 500 mL of 0.1 M HCNO added to 250 mL of 0.1 M KCNO
E) 500 mL of 0.1 M HCNO added to 250 mL of 0.1 M NaOH
2)
Ka(HCNO) = 2 ´ 10‒4.
pKa = - log Ka = - log (2 ´* 10^‒4.) = 3.70
500 mL of 0.1 M HCNO = 0.500 L * 0.1 mole / L = 0.050 mole.
and
mole of NaOH = 0.250 L * 0.1 mole / L = 0.025 mole.
HCNO + NaOH .............> NaCNO + H2O
mole of NaCNO = 0.025 mole.
and
mole of HCNO = (0.050 - 0.025) = 0.025 mole.
Using Henderson equation,
pH = pKa + log [salt] / [acid]
or
pH = 3.70 + log (0.025 / 0.025)
or
pH = 3.70 (answer)
Which solutions below would be described as a buffer solution? A) 500 mL of 0.1 M...
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