Chapter 5

A saturated solution of milk of magnesia, \(\mathrm{Mg}(\mathrm{OH})_{2},\) has a pH of \(10.5 .\) What is the hydrogen ion concentration of the solution? Is the solution acidic or basic?

What is the hydrogen ion concentration of a \(1.2 \times 10^{-4} \mathrm{M}\) solution of \(\mathrm{HClO}_{4} ?\) What is its pH?

What volume of \(0.109 \mathrm{M} \mathrm{HNO}_{3},\) in milliliters, is required to react completely with \(2.50 \mathrm{g}\) of \(\mathrm{Ba}(\mathrm{OH})_{2} ?\) $$2 \mathrm{HNO}_{3}(\mathrm{aq})+\mathrm{Ba}(\mathrm{OH})_{2}(\mathrm{s}) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})$$

What mass of \(\mathrm{Na}_{2} \mathrm{CO}_{3},\) in grams, is required for complete reaction with \(50.0 \mathrm{mL}\) of \(0.125 \mathrm{M} \mathrm{HNO}_{3} ?\) \(\mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq})+2 \mathrm{HNO}_{3}(\mathrm{aq}) \longrightarrow\) $$2 \mathrm{NaNO}_{3}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)$$

When an electric current is passed through an aqueous solution of NaCl, the valuable industrial chemicals \(\mathrm{H}_{2}(\mathrm{g})\) \(\mathrm{Cl}_{2}(\mathrm{g}),\) and \(\mathrm{NaOH}\) are produced. $$2 \mathrm{NaCl}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\ell) \longrightarrow \mathrm{H}_{2}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g})+2 \mathrm{NaOH}(\mathrm{aq})$$ What mass of NaOH can be formed from \(15.0 \mathrm{L}\) of \(0.35 \mathrm{M}\) NaCl? What mass of chlorine is obtained?

Hydrazine, \(\mathrm{N}_{2} \mathrm{H}_{4},\) a base like ammonia, can react with an acid such as sulfuric acid. \(2 \mathrm{N}_{2} \mathrm{H}_{4}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \longrightarrow 2 \mathrm{N}_{2} \mathrm{H}_{5}^{+}(\mathrm{aq})+\mathrm{SO}_{4}^{2-}(\mathrm{aq})\) What mass of hydrazine reacts with \(250 .\) mL of \(0.146 \mathrm{M}\) \(\mathrm{H}_{2} \mathrm{SO}_{4} ?\)

You can dissolve an aluminum soft-drink can in an aqueous base such as potassium hydroxide. \(2 \mathrm{Al}(\mathrm{s})+2 \mathrm{KOH}(\mathrm{aq})+6 \mathrm{H}_{2} \mathrm{O}(\ell) \longrightarrow\) $$2 \mathrm{KAl}(\mathrm{OH})_{4}(\mathrm{aq})+3 \mathrm{H}_{2}(\mathrm{g})$$ If you place \(2.05 \mathrm{g}\) of aluminum in a beaker with \(185 \mathrm{mL}\) of \(1.35 \mathrm{M} \mathrm{KOH},\) will any aluminum remain? What mass of \(\mathrm{KAl}(\mathrm{OH})_{4}\) is produced?

What volume of \(0.750 \mathrm{M} \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2},\) in milliliters, is required to react completely with \(1.00 \mathrm{L}\) of \(2.25 \mathrm{M} \mathrm{NaCl}\) solution? The balanced equation is $$\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+2 \mathrm{NaCl}(\mathrm{aq}) \longrightarrow \mathrm{PbCl}_{2}(\mathrm{s})+2 \mathrm{NaNO}_{3}(\mathrm{aq})$$

What volume of 0.125 M oxalic acid, \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) is required to react with \(35.2 \mathrm{mL}\) of \(0.546 \mathrm{M} \mathrm{NaOH} ?\) $$\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(\mathrm{aq})+2 \mathrm{NaOH}(\mathrm{aq}) \longrightarrow \mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{aq})$$

What volume of \(0.812 \mathrm{M} \mathrm{HCl}\), in milliliters, is required to titrate \(1.45 \mathrm{g}\) of \(\mathrm{NaOH}\) to the equivalence point? \(\mathrm{NaOH}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \longrightarrow \mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{NaCl}(\mathrm{aq})\)

What volume of \(0.955 \mathrm{M} \mathrm{HCl}\), in milliliters, is required to titrate \(2.152 \mathrm{g}\) of \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) to the equivalence point? $$\mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq})+2 \mathrm{HCl}(\mathrm{aq}) \longrightarrow \mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{CO}_{2}(\mathrm{g})+2 \mathrm{NaCl}(\mathrm{aq})$$

If 38.55 mL of \(\mathrm{HCl}\) is required to titrate \(2.150 \mathrm{g}\) of \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) according to the following equation, what is the molarity of the HCl solution? $$\mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq})+2 \mathrm{HCl}(\mathrm{aq}) \longrightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)$$

Potassium hydrogen phthalate, \(\mathrm{KHC}_{8} \mathrm{H}_{4} \mathrm{O}_{4},\) is used to standardize solutions of bases. The acidic anion reacts with strong bases according to the following net ionic equation: \(\mathrm{HC}_{8} \mathrm{H}_{4} \mathrm{O}_{4}^{-}(\mathrm{aq})+\mathrm{OH}^{-}(\mathrm{aq}) \longrightarrow \mathrm{C}_{8} \mathrm{H}_{4} \mathrm{O}_{4}^{2-}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell)\) If a \(0.902-\mathrm{g}\) sample of potassium hydrogen phthalate is dissolved in water and titrated to the equivalence point with \(26.45 \mathrm{mL}\) of \(\mathrm{NaOH}\), what is the molar concentration of the NaOH?

You have \(0.954 \mathrm{g}\) of an unknown acid, \(\mathrm{H}_{2} \mathrm{A},\) which reacts with NaOH according to the balanced equation \(\mathrm{H}_{2} \mathrm{A}(\mathrm{aq})+2 \mathrm{NaOH}(\mathrm{aq}) \longrightarrow \mathrm{Na}_{2} \mathrm{A}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\ell)\) If 36.04 mI. of \(0.509 \mathrm{M} \mathrm{NaOH}\) is required to titrate the acid to the equivalence point, what is the molar mass of the acid?

A An unknown solid acid is either citric acid or tartaric acid. To determine which acid you have, you titrate a sample of the solid with NaOH. The appropriate reactions are as follows: Citric acid: \(\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(\mathrm{aq})+3 \mathrm{NaOH}(\mathrm{aq}) \longrightarrow\) $$ 3 \mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{Na}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(\mathrm{aq}) $$ Tartaric acid: \(\mathrm{H}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}(\mathrm{aq})+2 \mathrm{NaOH}(\mathrm{aq}) \longrightarrow\) $$2 \mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{Na}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}(\mathrm{aq})$$ A \(0.956-\mathrm{g}\) sample requires \(29.1 \mathrm{mL}\) of \(0.513 \mathrm{M} \mathrm{NaOH}\) for titration to the equivalence point. What is the unknown acid?

To analyze an iron-containing compound, you convert all the iron to \(\mathrm{Fe}^{2+}\) in aqueous solution and then titrate the solution with standardized \(\mathrm{KMnO}_{4}\). The balanced, net ionic equation is \(\mathrm{MnO}_{4}^{-}(\mathrm{aq})+5 \mathrm{Fe}^{2+}(\mathrm{aq})+8 \mathrm{H}^{+}(\mathrm{aq}) \longrightarrow\) $$\mathrm{Mn}^{2+}(\mathrm{aq})+5 \mathrm{Fe}^{3+}(\mathrm{aq})+4 \mathrm{H}_{2} \mathrm{O}(\ell) $$ A \(0.598-\mathrm{g}\) sample of the iron-containing compound requires \(22.25 \mathrm{mL}\) of \(0.0123 \mathrm{M} \mathrm{KMnO}_{4}\) for titration to the equivalence point. What is the mass percent of iron in the sample?

Vitamin C is the simple compound \(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6}\). Besides being an acid, it is a reducing agent. One method for determining the amount of vitamin C in a sample is therefore to titrate it with a solution of bromine, \(\mathbf{B r}_{2},\) an oxidizing agent. \(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6}(\mathrm{aq})+\mathrm{Br}_{2}(\mathrm{aq}) \longrightarrow 2 \mathrm{HBr}(\mathrm{aq})+\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{O}_{6}(\mathrm{aq})\) A \(1.00-\mathrm{g}\) " chewable" vitamin C tablet requires \(27.85 \mathrm{mL}\) of \(0.102 \mathrm{M} \mathrm{Br}_{2}\) for titration to the equivalence point. What is the mass of vitamin C in the tablet?

Give the formula for the following: (a) a soluble compound containing the bromide ion (b) an insoluble hydroxide (c) an insoluble carbonate (d) a soluble nitrate-containing compound

Which of the following copper(11) salts are soluble in water and which are insoluble: \(\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}, \mathrm{CuCO}_{3}\) \(\mathrm{Cu}_{3}\left(\mathrm{PO}_{4}\right)_{2}, \mathrm{CuCl}_{2} ?\)

Name two anions that combine with \(\mathrm{Al}^{3+}\) ion to produce water- soluble compounds.

Identify the spectator ion or ions in the reaction of nitric acid and magnesium hydroxide, and write the net ionic equation. What type of exchange reaction is this? $$\begin{aligned} 2 \mathrm{H}^{+}(\mathrm{aq})+2 \mathrm{NO}_{3}^{-}(\mathrm{aq})+\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s}) \longrightarrow & \\ 2 \mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{Mg}^{2+}(\mathrm{aq})+2 \mathrm{NO}_{3}^{-}(\mathrm{aq})\end{aligned}$$

Identify the water-insoluble product in each reaction and write the net ionic equation: (a) \(\operatorname{CuCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{S}(\mathrm{aq}) \longrightarrow \mathrm{CuS}+2 \mathrm{HCl}\) (b) \(\operatorname{CaCl}_{2}(\mathrm{aq})+\mathrm{K}_{2} \mathrm{CO}_{3}(\mathrm{aq}) \longrightarrow 2 \mathrm{KCl}+\mathrm{Ca} \mathrm{CO}_{3}\) (c) \(\mathrm{AgNO}_{3}(\mathrm{aq})+\mathrm{NaI}(\mathrm{aq}) \longrightarrow \mathrm{AgI}+\mathrm{NaNO}_{3}\)

Bromine is obtained from sea water by the following reaction: $$\mathrm{Cl}_{2}(\mathrm{g})+2 \mathrm{NaBr}(\mathrm{aq}) \longrightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{Br}_{2}(\ell)$$ (a) What has been oxidized? What has been reduced? (b) Identify the oxidizing and reducing agents. (c) What mass of \(\mathrm{Cl}_{2}\) is required to react completely with \(125 \mathrm{mL}\) of \(0.153 \mathrm{M} \mathrm{NaBr} ?\)

Identify each of the following substances as an oxidizing or reducing agent: \(\mathrm{HNO}_{3}, \mathrm{Na}, \mathrm{Cl}_{2}, \mathrm{O}_{2}, \mathrm{KMnO}_{4}\).

Which contains the greater mass of solute: 1 I. of \(0.1 \mathrm{M}\) NaCl or 1 L of \(0.06 \mathrm{M} \mathrm{Na}_{2} \mathrm{CO}_{3} ?\)

You have a bottle of solid \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) and a \(500.0-\mathrm{mL}\). volumetric flask. Explain how you would make a \(0.20 \mathrm{M}\) solution of sodium carbonate.

You have 0.500 mol of \(\mathrm{KCl}\), some distilled water, and a \(250 .-\mathrm{mL}\) volumetric flask. Describe how you would make a \(0.500 \mathrm{M}\) solution of \(\mathrm{KCl}\).

Which has the larger concentration of hydrogen ions, \(0.015 \mathrm{M} \mathrm{HCl}\) or a hydrochloric acid solution with a \(\mathrm{pH}\) of \(1.2 ?\)

What volume of \(0.054 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) is required to react completely with \(1.56 \mathrm{g}\) of \(\mathrm{KOH} ?\)

Ammonium sulfide, (NH,) \(_{2} \mathrm{S}\), reacts with \(\mathrm{Hg}\left(\mathrm{NO}_{3}\right)_{2}\) to produce HgS and \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) (a) Write the overall balanced equation for the reaction. Indicate the state (s, aq) for each compound. (b) Name each compound. (c) What type of reaction is this?

What species (atoms, molecules, or ions) are present in an aqueous solution of each of the following compounds? (a) \(\mathrm{NH}_{3}\) (c) \(\mathrm{NaOH}\) (b) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) (d) HBr

Suppose an Alka-Seltzer tablet contains exactly 100 mg of citric acid, \(\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7},\) plus some sodium bicarbonate. If the following reaction occurs, what mass of sodium bicarbonate must the tablet also contain? \(\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(\mathrm{aq})+3 \mathrm{NaHCO}_{3}(\mathrm{aq}) \longrightarrow\) $$3 \mathrm{H}_{2} \mathrm{O}(\ell)+3 \mathrm{CO}_{2}(\mathrm{g})+\mathrm{Na}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(\mathrm{aq}) $$

A Sodium bicarbonate and acetic acid react according to the equation \(\mathrm{NaHCO}_{3}(\mathrm{aq})+\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq}) \longrightarrow\) $$\mathrm{NaCH}_{3} \mathrm{CO}_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)$$ What mass of sodium acetate can be obtained from mixing \(15.0 \mathrm{g}\) of \(\mathrm{NaHCO}_{3}\) with \(125 \mathrm{mL}\) of \(0.15 \mathrm{M}\) acetic acid?

A noncarbonated soft drink contains an unknown amount of citric acid, \(\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7} .\) If \(100 .\) mL of the soft drink requires \(33.51 \mathrm{mL}\) of \(0.0102 \mathrm{M} \mathrm{NaOH}\) to neutralize the citric acid completely, what mass of citric acid does the soft drink contain per \(100 .\) mL? The reaction of citric acid and \(\mathrm{NaOH}\) is \mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(\mathrm{aq})+3 \mathrm{NaOH}(\mathrm{aq}) \longrightarrow \mathrm{Na}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(\mathrm{aq})+3 \mathrm{H}_{2} \mathrm{O}(\ell)

Sodium sulfate, \(\mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3},\) is used as a "fixer" in black-and-white photography. Suppose you have a bottle of sodium sulfate and want to determine its purity. The thiosulfate ion can be oxidized with \(\mathrm{I}_{2}\) according to the balanced, net ionic equation \(\mathrm{I}_{2}(\mathrm{aq})+2 \mathrm{S}_{2} \mathrm{O}_{3}^{2-}(\mathrm{aq}) \longrightarrow 2 \mathrm{I}^{-}(\mathrm{aq})+\mathrm{S}_{4} \mathrm{O}_{6}^{2-}(\mathrm{aq})\) If you use \(40.21 \mathrm{mL}\) of \(0.246 \mathrm{M} \mathrm{I}_{2}\) in a titration, what is the weight percent of \(\mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3}\) in a \(3.232-\mathrm{g}\) sample of impure material?

You have a \(4.554-\mathrm{g}\) sample that is a mixture of oxalic acid, \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4},\) and another solid that does not react with sodium hydroxide. If \(29.58 \mathrm{mL}\) of \(0.550 \mathrm{M} \mathrm{NaOH}\) is required to titrate the oxalic acid in the 4.554 -g sample to the equivalence point, what is the weight percent of oxalic acid in the mixture? Oxalic acid and NaOH react according to the equation $$\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(\mathrm{aq})+2 \mathrm{NaOH}(\mathrm{aq}) \longrightarrow \mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\ell)$$

(a) Name two water-soluble compounds containing the \(\mathrm{Cu}^{2+}\) ion. Name two water-insoluble compounds based on the \(\mathrm{Cu}^{2+}\) ion. (b) Name two water-soluble compounds containing the Ba \(^{2+}\) ion. Name two water-insoluble compounds based on the \(\mathrm{Ba}^{2+}\) ion.

Balance these reactions and then classify each one as a precipitation, acid- base, or gas-forming reaction. Show states for the products \((\mathrm{s}, \ell, \mathrm{g}, \mathrm{aq}),\) and write the net ionic equation. (a) \(\mathrm{K}_{2} \mathrm{CO}_{3}(\mathrm{aq})+\mathrm{HClO}_{4}(\mathrm{aq}) \longrightarrow \mathrm{KClO}_{4}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{FeCl}_{2}(\mathrm{aq})+\left(\mathrm{NH}_{4}\right)_{2} \mathrm{S}(\mathrm{aq}) \longrightarrow \mathrm{FeS}+\mathrm{NH}_{4} \mathrm{Cl}\) (c) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq}) \longrightarrow \mathrm{FeCO}_{3}+\mathrm{NaNO}_{3}\)

For each reaction, write an overall, balanced equation and the net ionic equation. (a) the reaction of aqueous lead(II) nitrate and aqueous potassium hydroxide (b) the reaction of aqueous copper(II) nitrate and aqueous sodium carbonate

(a) What is the pH of a 0.105 M HCl solution? (b) What is the hydrogen ion concentration in a solution with a pH of \(2.56 ?\) Is the solution acidic or basic? (c) A solution has a pH of 9.67. What is the hydrogen ion concentration in the solution? Is the solution acidic or basic? (d) \(A 10.0\) -mL. sample of \(2.56 \mathrm{M}\) HCl is diluted with water to \(250 .\) mL. What is the pH of the dilute solution?

A solution of hydrochloric acid has a volume of \(125 \mathrm{mL}\) end a pH of \(2.56 .\) What mass of \(\mathrm{NaHCO}_{3}\) must be added to completely consume the HCl?

A One-half liter \((500 . \mathrm{mL})\) of \(2.50 \mathrm{M} \mathrm{HCl}\) is mixed with \(250 .\) mL of \(3.75 \mathrm{M} \mathrm{HCl}\). Assuming the total solution volume after mixing is \(750 . \mathrm{mL}\), what is the concentration of hydrochloric acid in the resulting solution? What is its \(\mathrm{pH} ?\)

A solution of hydrochloric acid has a volume of \(250 .\) mL and a pH of \(1.92 .\) Exactly \(250 .\) mL of \(0.0105 \mathrm{M} \mathrm{NaOH}\) is added. What is the pH of the resulting solution?

Suppose you dilute \(25.0 \mathrm{mL}\) of a \(0.110 \mathrm{M}\) solution of \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) to exactly \(100.0 \mathrm{mL}\). You then take exactly \(10.0 \mathrm{mL}\) of this diluted solution and add it to a \(250-\mathrm{mL}\) volumetric flask. After filling the volumetric flask to the mark with distilled water (indicating the volume of the new solution is exactly \(250 \mathrm{mL}\) ), what is the concentration of the diluted \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) solution?

On General ChemistryNow CD-ROM or website Screen 4.12, Chemical Puzzler, you can explore the reaction of baking soda (NaHCO \(_{3}\) ) with the acetic acid in vinegar. Suppose you place exactly 200 mL. of vinegar in the beaker and add baking soda. The reaction occurring is \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq})+\mathrm{NaHCO}_{3}(\mathrm{aq}) \longrightarrow\) $$\mathrm{NaCH}_{3} \mathrm{CO}_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)$$ How many spoonfuls of baking soda is required to consume the acetic acid in the \(200-\mathrm{mL}\). sample? (Assume there is \(50.0 \mathrm{g}\) of acetic acid per liter of vinegar and a spoonful of baking soda has a mass of \(3.8 \mathrm{g} .\) ) Are three spoonfuls sufficient? Are four spoonfuls enough?

A You place \(2.56 \mathrm{g}\) of \(\mathrm{CaCO}_{3}\) in a beaker containing 250\. mL of 0.125 M HC1 (Figure 5.5). When the reaction has ceased, does any calcium carbonate remain? What mass of \(\mathrm{CaCl}_{2}\) can be produced? $$\mathrm{CaCO}_{3}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \longrightarrow \mathrm{CaCl}_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)$$

A compound has been isolated that can have either of two possible formulas: (a) \(\mathrm{K}\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right]\) or (b) \(\mathrm{K}_{3}\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right] .\) To find which is correct, you dissolve a weighed sample of the compound in acid and then titrate the oxalate ion \(\left(\mathrm{C}_{2} \mathrm{O}_{4}^{2}\right)\) that comes from the compound with potassium permanganate, \(\mathrm{KMnO}_{4}\) (the source of the \(\mathrm{MnO}_{4}^{-}\) ion). The balanced, net ionic equation for the titration is $$\begin{array}{rl}5 \mathrm{C}_{2} \mathrm{O}_{4}^{2-}(\mathrm{aq})+2 \mathrm{MnO}_{4}^{-}(\mathrm{aq})+16 \mathrm{H}^{+}(\mathrm{aq}) & \longrightarrow \\\2 \mathrm{Mn}^{2+}(\mathrm{aq})+10 \mathrm{CO}_{2}(\mathrm{g})+8 & \mathrm{H}_{2} \mathrm{O}(\ell) \end{array}$$ Titration of \(1.356 \mathrm{g}\) of the compound requires \(34.50 \mathrm{mL}\) of \(0.108 \mathrm{M} \mathrm{KMnO}_{4} .\) Which is the correct formula of the iron-containing compound: (a) or (b)?

A The cancer chemotherapy drug cisplatin, \(\operatorname{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\) can be made by reacting (NH_) \(_{2} \mathrm{PtCl}_{4}\) with ammonia in aqueous solution. Besides cisplatin, the other product is \(\mathrm{NH}_{1} \mathrm{Cl}\) (a) Write a balanced equation for this reaction. (b) To obtain \(12.50 \mathrm{g}\) of cisplatin, what mass of \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{PtCl}_{4}\) is required? What volume of \(0.125 \mathrm{M}\) \(\mathrm{NH}_{3}\) is required? (c) Cisplatin can react with the organic compound pyridine, \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N},\) to form a new compound. $$\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}(\mathrm{aq})+x \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}(\mathrm{aq}) \longrightarrow \mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\left(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\right)_{x}(\mathrm{s})$$ Suppose you treat \(0.150 \mathrm{g}\) of cisplatin with what you believe is an excess of liquid pyridine \((1.50 \mathrm{mL}\) \(d=0.979 \mathrm{g} / \mathrm{mL}) .\) When the reaction is complete, you can find out how much pyridine was not used by titrating the solution with standardized HCl. If 37.0 mL. of \(0.475 \mathrm{M} \mathrm{HCl}\) is required to titrate the excess pyridine, \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \longrightarrow \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})\) what is the formula of the unknown compound \(\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\left(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{N}\right)_{x} ?\)

You need to know the volume of water in a small swimming pool, but, owing to the pool's irregular shape, it is not a simple matter to determine its dimensions and calculate the volume. To solve the problem you stir in a solution of a dye \(\left(1.0 \mathrm{g} \text { of methylene blue, } \mathrm{C}_{16} \mathrm{H}_{18} \mathrm{Cl} \mathrm{N}_{3} \mathrm{S}\right.\) in 50.0 mL of water). After the dye has mixed with the water in the pool, you take a sample of the water. Using an instrument such as a spectrophotometer, you determine that the concentration of the dye in the pool is 4.1 \(\times 10^{-8}\) M. What is the volume of water in the pool?

A In some laboratory analyses the preferred technique is to dissolve a sample in an excess of acid or base and then "back-titrate" the excess with a standard base or acid. This technique is used to assess the purity of a sample of \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} .\) Suppose you dissolve a \(0.475-\mathrm{g}\) sample of impure (NH_) \(_{2} \mathrm{SO}_{4}\) in aqueous KOH. \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}(\mathrm{aq})+\mathrm{KOH}(\mathrm{aq}) \longrightarrow\) $$ \mathrm{NH}_{3}(\mathrm{aq})+\mathrm{K}_{2} \mathrm{SO}_{4}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\ell) $$ The \(\mathrm{NH}_{3}\) liberated in the reaction is distilled from the solution into a flask containing \(50.0 \mathrm{mL}\), of \(0.100 \mathrm{M} \mathrm{HCl}\). The ammonia reacts with the acid to produce \(\mathrm{NH}_{4} \mathrm{Cl}\) but not all of the \(\mathrm{HCl}\) is used in this reaction. The amount of excess acid is determined by titrating the solution with standardized NaOH. This titration consumes 11.1 mL of 0.121 M NaOH. What is the weight percent of \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\) in the \(0.475-\mathrm{g}\) sample?