Chapter 9: Q43P (page 210)

Calculate how many milliliters of $0.626 MKOH$ should be added to $5.00 g$ of MOBS (Table 9-2) to give a pH of 7.40.

Short Answer

Expert verified

$16.2 mL$ of $0.626 MKOH$ should be added to $5.00 g$ of MOBS to give a pH of $7.40$ .

Step by step solution

Concept used.

The pH of the buffer determined by the concentration ratio of $[A^{-}] and [HA]$ by the following Henderson-Hasselbalch equation: localid="1654948500333" $pH = {pK}_{a} + \log [A^{-}] / [HA]$ .

The milliliters of 0.626MKOH should be added to 5.00g of MOBS to give a pH of 7.40 .

Calculate the moles of MOBS by the following:

$M (MOBS) = 223.29 g / molm (MOBS) = 5 g n (MOBS) = m / M = 0.0224 mol$

Consider the following reaction:

$HA + {OH}^{-} \to A^{-} + H_{2} O [HA] = 0.0224 - x [A^{-}] = x$

The pH of the buffer depends on the concentration ratio of $[A^{-}]$ and $[HA]$ by the following Henderson-Hasselbach equation

$pH = {pK}_{a} + \log ([A^{-}] / [HA]) 7.40 = 7.48 + \log (x / (0.0224 - x)) x = 0.01017 mol$

Now calculate the volume of $0.626 MKOH$ by the following:

$volume = moles / concentration = 0.01017 mol / 0.626 M = 16.2 ml$

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Calculate how many milliliters of $0.626 MKOH$ should be added to $5.00 g$ of MOBS (Table 9-2) to give a pH of 7.40.

Short Answer

Step by step solution

Concept used.

The milliliters of 0.626MKOH should be added to 5.00g of MOBS to give a pH of 7.40 .

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Calculate how many milliliters of 0.626MKOHshould be added to 5.00g of MOBS (Table 9-2) to give a pH of 7.40.

Short Answer

Step by step solution

Concept used.

The milliliters of 0.626MKOH should be added to 5.00g of MOBS to give a pH of 7.40 .

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Chemistry Textbooks

Chemical Analysis

Organic Chemistry

Ionic and Molecular Compounds

Making Measurements

Physical Chemistry

Chemistry Branches

Study anywhere. Anytime. Across all devices.

Calculate how many milliliters of $0.626 MKOH$ should be added to $5.00 g$ of MOBS (Table 9-2) to give a pH of 7.40.