A 1.0-L buffer solution is 0.125 M in HNO2 and 0.155 M in NaNO2. Part A Determin

Question

A 1.0-L buffer solution is 0.125 M in HNO2 and 0.155 M in NaNO2.

Part A

Determine the concentrations of HNO2 and NaNO2 after addition of 1.8 g HCl.

Express your answers using three significant figures separated by a comma.

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Part B

Determine the concentrations of HNO2 and NaNO2 after addition of 1.8 g NaOH.

Express your answers using three significant figures separated by a comma.

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Part C

Determine the concentrations of HNO2 and NaNO2 after addition of 1.8 g HI.

Express your answers using three significant figures separated by a comma.

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Explanation / Answer

PART A)

moles of acid HNO2 = 0.125 x 1 = 0.125

salt NaNO2 moles = 0.155 x 1 = 0.155

HCl moles = 1.8 / 36.5 = 0.0493

on addition of strong acid to acidic buffer, acid concentration increases and salt concentration decreases                               

HNO2 moles = 0.125 + 0.0493 =0.1743

HNO2 concentration = 0.1743 M

NaNO2 moles = 0.155 - 0.0493 = 0.1057

NaNO2 concentration   = 0.1057 M

prat B )

moles of NaOH = 1.8 / 40 = 0.045

on addition base to acidic buffer acid concentration decreases and salt concentration increases

[HNO2] = 0.125 -0.045 = 0.08 M

[NaNO2] = 0.155 + 0.045 = 0.2 M

Part C )

mass = 1.8 g

molar mass of HI = 127.9 g/mol

moles = 1.8 / 127.9

           = 0.0140

[HNO2] = 0.125 + 0.0140 = 0.139 M

[NaNO2] = 0.155 - 0.0140 = 0.141 M

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