Asked Jun 4, 2019

A buffer solution contains 0.254 M NaHSO3 and 0.348 M Na2SO3

If 0.0285 moles of hydroiodic acid are added to 250 mL of this buffer, what is the pH of the resulting solution ? 
(Assume that the volume change does not change upon adding hydroiodic acid)


Expert Answer

Step 1

A buffer resists a considerable change in pH when a small amount of acid or base is added to it. The behaviour of a buffer is described by the Henderson-Hasselbalch equation. The Henderson-Hasselbalch equation for a mixture of weak acids and their salts is shown in equation (1).

The standard  pKa value for HSO3- is 7.19.

Step 2

The relation between litter and millilitre is as follows:

1L = 1000 mL


250 mL = 0.250 L

Calculate the number of moles of NaHSO3 and Na2SO3.

The product of volume and concentration gives the number of moles, which is expressed by equation (2).

For NaHSO3,

Substitute 0.250 L for volume and 0.254 M for concentration in equation (2) as shown in equation (3).

For Na2SO3,

Substitute 0.250 L for volume and 0.348 M for concentration in equation (2) as shown in equation (4).

Step 3

The reaction between buffer solution and HI is represented by equation (5).

Using the IC...


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