# What is the pH of a buffer that was prepared by adding 3.96 g of sodium benzoate, #NaC_7H_5O_2#, to 1.00 L of 0.0100 M benzoic acid, #HC_7H_5O_2#?

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Assume that there is no change in volume. The #K_a# for benzoic acid is #6.3 * 10^-5# .

Assume that there is no change in volume. The

##### 1 Answer

The

#### Explanation:

Let's represent the benzoate ion,

Then the equation for the dissociation of benzoic acid becomes

The typical formula for calculating the **Henderson-Hasselbalch equation**:

#color(blue)(|bar(ul("pH"= "p"K_"a" + log (("[A"^"-""]")/"[HA]"))|)#

Our job is to calculate the numbers to insert into the formula.

**(a)**

**(b)**

∴

**(c)**

Now, we insert these values into the Henderson-Hasselbalch equation.

The