A chemistry graduate student is given 125. mL of a 1.70 M chlorous acid (HNO2) solution. Chlorous acid is a weak acid with Ka= 1.1 x 10^-2. What mass of NaClO2 should the student dissolve in the HClO2 solution to turn it into a buffer with pH = 2.48? You may assume that the volume of the solution doesn't change when the NaClO2 is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits.
pH of buffer is calculated using Hendersen equation as
pH = pKa + log [conjugate base] /[acid]
given [acid] = 1.70M
and ka of acid = 1.1 x10-2 , thus pKa of acid = 1.96
we need to calculate [conjugate base]
thus substituting the known values
2.48 = 1.96 + log [conjugate base]/ 1.7
ccalclulating we get molarity of NaCLO2 = 5.6287 M
Thus 1000mL of buffer should contain mass of NaClO2 = molarity x molar mass
= 5.6287mol/L x 90.44 g/mol
= 509.06g/L
But our buffer is made of 125mL only.
Thus the mass of NaClO2 to be added to 125mL of buffer = 509.06g/L x 0.125L
= 63.63 g
= 64 g ( rounding to two significant figures)
A chemistry graduate student is given 125. mL of a 1.70 M chlorous acid (HNO2) solution....
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A chemistry graduate student is given 450. mL of a 0.90 M nitrous acid (HNO2) solution. Nitrous acid is a weak acid with K-4.5x10 . What mass o KNO2 should the student dissolve in the HNO2 solution to turn it into a buffer with pH-3.20? You may assume that the volume of the solution doesn't change when the KNO2 is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits.
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