Chapter 4

How many milliliters of \(0.100 \mathrm{M} \mathrm{NaOH}\) are needed to completely neutralize \(25.0 \mathrm{~mL}\) of \(0.250 \mathrm{M} \mathrm{H}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6} ?\) The reaction is $$ 2 \mathrm{NaOH}(a q)+\mathrm{H}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}(a q) \stackrel{\longrightarrow}{\mathrm{Na}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}(a q)+2 \mathrm{H}_{2} \mathrm{O}} $$

What is the molarity of an aqueous solution of potassium hydroxide if \(21.34 \mathrm{~mL}\) is exactly neutralized by \(20.78 \mathrm{~mL}\) of \(0.116 M \mathrm{HCl}\) ? Write and balance the molecular equation for the reaction.

How many grams of baking soda, \(\mathrm{NaHCO}_{3}\), are needed to react with \(162 \mathrm{~mL}\) of stomach acid having an \(\mathrm{HCl}\) concentration of \(0.052 \mathrm{M}\) ?

How many grams of cobalt(II) chloride are needed to react completely with \(60.0 \mathrm{~mL}\) of \(0.200 \mathrm{M} \mathrm{KOH}\) solution? The net ionic equation for the reaction is $$ \mathrm{Co}^{2+}(a q)+2 \mathrm{OH}^{-}(a q) \longrightarrow \mathrm{Co}(\mathrm{OH})_{2}(s) $$

Suppose \(3.50 \mathrm{~g}\) of solid \(\mathrm{Mg}(\mathrm{OH})_{2}\) is added to \(30.0 \mathrm{~mL}\) of \(0.500 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) solution. What will the concentration of \(\mathrm{Mg}^{2+}\) be when all of the acid has been neutralized? How many grams of \(\mathrm{Mg}(\mathrm{OH})_{2}\) will not have dissolved?

In a titration, \(23.25 \mathrm{~mL}\) of \(0.105 \mathrm{M} \mathrm{NaOH}\) was needed to react with \(21.45 \mathrm{~mL}\) of \(\mathrm{HCl}\) solution. What is the molarity of the acid?

A 12.5 mL sample of vinegar, containing acetic acid, was titrated using \(0.504 \mathrm{M} \mathrm{NaOH}\) solution. The titration required \(20.65 \mathrm{~mL}\) of the base. What was the molar concentration of acetic acid in the vinegar?

Lactic acid, \(\mathrm{HC}_{3} \mathrm{H}_{5} \mathrm{O}_{3},\) is a monoprotic acid that forms when milk sours. An \(18.5 \mathrm{~mL}\) sample of a solution of lactic acid required \(17.25 \mathrm{~mL}\) of \(0.155 \mathrm{M} \mathrm{NaOH}\) to reach an end point in a titration. (a) How many moles of lactic acid were in the sample? (b) How many grams of lactic acid were in the sample?

Oxalic acid, a diprotic acid having the formula \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\), is used to clean the rust out of radiators in cars. A sample of an oxalic acid mixture was analyzed by titrating a 0.1000 g sample dissolved in water with \(0.0200 M\) \(\mathrm{NaOH}\). A volume of \(15.20 \mathrm{~mL}\) of the base was required to completely neutralize the oxalic acid. What was the percentage by mass of oxalic acid in the sample?

A certain lead ore contains the compound \(\mathrm{PbCO}_{3} .\) A sample of the ore weighing \(1.526 \mathrm{~g}\) was treated with nitric acid, which dissolved the \(\mathrm{PbCO}_{3}\). The resulting solution was filtered from undissolved rock and required \(29.22 \mathrm{~mL}\) of \(0.122 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4}\) to completely precipitate all of the lead as \(\mathrm{PbSO}_{4}\). (a) How many moles of lead were in the ore sample? (b) How many grams of lead were in the ore sample? (c) What is the percentage by mass of lead in the ore? (d) Would you expect the same results if the solid \(\mathrm{PbSO}_{4}\) was collected, washed, dried, and weighed and the final mass was used to answer this question?