Question

A 1.00 l solution contains 24.52 g of nitrous acid, hno2. what mass of sodium nitrite, nano2, should be added to it to make a buffer with a ph of 2.96

Answer 1

To make a buffer solution with a pH of 2.96, calculate the concentration of nitrous acid and use the Henderson-Hasselbalch equation to find the mass of sodium nitrite required.

Step-by-step explanation:

To make a buffer solution with a pH of 2.96, we need to calculate the mass of sodium nitrite (NaNO2) that should be added to the 1.00 L solution containing 24.52 g of nitrous acid (HNO2). First, calculate the concentration of nitrous acid using the formula moles = mass / molar mass. Then, use the equation for the pH of a weak acid solution, pH = -log[H+], to find the hydrogen ion concentration. Finally, use the Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), to calculate the mass of sodium nitrite required to achieve the desired pH.

Answer 2

when moles of HNO2 = mass/molar mass

=24.52 g / 47g/mol

= 0.52 mol

[HNO2] = moles / volume

= 0.52 mol * 1 L

= 0.52 M

by using H-H equation:

PH = Pka + ㏒[salt / acid]

when we have Ka = 4 x 10^-4

∴Pka = - ㏒Ka

= -㏒(4x 10^-4)

= 3.4

by substitution in H-H equation:

2.96 = 3.4 + ㏒[NaNO2/0.52]

∴[NaNO2] = 0.189 M

when moles NaNO2 = 0.189 M* 1 L = 0.189 mol

∴Mass of NaNO2 = moles NaNO2 * molar mass

= 0.189 mol * 68.99g/mol

= 13 g