Calculate the pH of a buffer solution prepared by dissolving 19.50 g of sodium cyanate NaCNO (65.01g/mol) in 1.00 M cyanic acid (HCNO) to a final volume of 1.00 liter of solution. Ka(HCNO) = 3.50 x 10-4
mass(NaCNO)= 19.50 g
use:
number of mol of NaCNO,
n = mass of NaCNO/molar mass of NaCNO
=(19.5 g)/(65.01 g/mol)
= 0.3 mol
volume , V = 1 L
use:
Molarity,
M = number of mol / volume in L
= 0.3/1
= 0.3 M
Ka = 3.5*10^-4
pKa = - log (Ka)
= - log(3.5*10^-4)
= 3.456
use:
pH = pKa + log {[conjugate base]/[acid]}
= 3.456+ log {0.3/1}
= 2.933
Answer: 2.93
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