Three Major Classes of Chemical Reactions

Explain why an oxidizing agent undergoes reduction.

Which of the following scenes best represents how the ions occur in an aqueous solution of:

a. $\mathit{C}\mathit{a}\mathit{C}{\mathit{l}}_{\mathbf{2}}$ b. $\mathit{L}{\mathit{i}}_{\mathbf{2}}\mathit{S}{\mathit{O}}_{\mathbf{4}}$ c. $\mathit{N}{\mathit{H}}_{\mathbf{4}}\mathit{B}\mathit{r}\mathbf{?}$

What two factors cause water to be polar?

What must be present in an aqueous solution for it to conduct an electric current? What general classes of compounds form solutions that conduct?

What occurs on the molecular level when an ionic compound dissolves in water?

Question: How many moles and numbers of ions of each type are present in the following aqueous solutions? 

(a) 130 mL of 0.45 M aluminum chloride

(b) 9.80 mL of a solution containing 2.59 g lithium sulfate/L 

(c) 245 mL of a solution containing  formula units of potassium bromide per liter.

How many moles and numbers of ions of each type are present in the following aqueous solutions? 

(a) 88 mL of 1.75 M magnesium chloride 

(b) 321 mL of a solution containing 0.22 g aluminum sulfate/L 

(c) 1.65 L of a solution containing 8.83 x 10²¹ formula units of cesium nitrate per liter.

Question: How many total moles of ions are released when each of the following samples dissolves completely in water? (a) 0.32 mol of   (b) 25.4 g of  (c)   formula units of LiCl

Why are some covalent compounds soluble in water and others are not?

How many total moles of ions are released when each of the following samples dissolves completely in water?(a) 0.75 mol of ${\mathbf{\text{K}}}_{\mathbf{\text{3}}}{\mathbf{\text{PO}}}_{\mathbf{\text{4}}}$  (b)  ${\mathbf{\text{6.88×10}}}^{\mathbf{\text{-3}}}$ g of ${\mathbf{\text{NiBr}}}_{\mathbf{\text{2}}}{\mathbf{\text{.3H}}}_{\mathbf{\text{2}}}\mathbf{\text{O}}$ (c)  ${\mathbf{\text{2.23×10}}}^{\mathbf{\text{22}}}$ formula units of ${\mathbf{\text{FeCl}}}_{\mathbf{\text{3}}}$

To study a marine organism, a biologist prepares a 1.00-kg sample to simulate the ion concentrations in seawater. She mixes 26.5 g of NaCl, 2.40 g of MgCl2, 3.35 g of MgSO4, 1.20 g of CaCl2, 1.05 g of KCl, 0.315 g of NaHCO3, and 0.098 g of NaBr in distilled water. 

(a) If the density of the solution is 1.025 g/cm3, what is the molarity of each ion? 

(b) What is the total molarity of alkali metal ions? 

(c) What is the total molarity of alkaline earth metal ions? 

(d) What is the total molarity of anions?

Water “softeners” remove metal ions such as  and  by replacing them with enough   ions to maintain the same number of positive charges in the solution. If 1.0 x 10³ L of “hard” water is 0.015 M  and 0.0010 M  how many moles of   are needed to replace these ions?

Question: How many moles of  ions are present in the following aqueous solutions?

(a) 1.4 mL of 0.75 M hydrobromic acid 

(b) 2.47 mL of 1.98 M hydriodic acid 

(c) 395 mL of 0.270 M nitric acid

Question: How many moles of H⁺ ions are present in the following aqueous solutions?

(a) 1.40 L of 0.25 M perchloric acid 

(b) 6.8 mL of 0.92 M nitric acid 

(c) 2.6 L of 0.085 M hydrochloric acid

Question: State whether an aqueous solution of each of the following substances conducts an electric current. Explain your reasoning. 

(a) Potassium sulfate (b) Sucrose, ${\mathit{C}}_{\mathbf{12}}{\mathit{H}}_{\mathbf{22}}{\mathit{O}}_{\mathbf{11}}$

Question: State whether an aqueous solution of each of the following substances conducts an electric current. Explain your reasoning. 

(a) Caesium bromide (b) Hydrogen iodide

Question: State whether each of the following substances is likely to be very soluble in water. Explain.

(a) Benzene, C₆H₆ (b) Sodium hydroxide (c) Ethanol, CH₂CH₂OH

(d) Potassium acetate.

Why are some ionic compounds soluble in water and others are not?

Question: Which of the following scenes best represents a volume from a solution of magnesium nitrate?

State whether each of the following substances is likely to be very soluble in water. Explain.

(a) Lithium nitrate 

(b) Glycine   $\left(H_2{\mathrm{NCH}}_2\mathrm{COOH}\right)$

(c) Pentane 

(d) Ethylene glycol $\left({\mathrm{HOCH}}_2{\mathrm{CH}}_2\mathrm{OH}\right)$

How many total moles of ions are released when each of the following samples dissolves completely in water? 

(a) 0.805 mol of  ${\mathbf{\text{Rb}}}_{\mathbf{\text{2}}}{\mathbf{\text{SO}}}_{\mathbf{\text{4}}}$ (b) ${\mathbf{\text{3.85×10}}}^{\mathbf{\text{-3}}}$  g of  $\mathbf{\text{Ca }}{\left({\text{NO}}_{\text{3}}\right)}_{\mathbf{\text{2}}}$

(c)  ${\mathbf{\text{4.03×10}}}^{\mathbf{\text{19}}}$ Formula units of $\mathbf{\text{Sr }}{\left({\text{HCO}}_{\text{3}}\right)}_{\mathbf{\text{2}}}$

How many total moles of ions are released when each of the following samples dissolves completely in water?

(a) 0.734 mol of ${\mathbf{\text{Na}}}_{\mathbf{\text{2}}}{\mathbf{\text{HPO}}}_{\mathbf{\text{4}}}$                                 

  (b) 3.86 g of ${\mathbf{\text{CuSO}}}_{\mathbf{\text{4}}}{\mathbf{\text{.5H}}}_{\mathbf{\text{2}}}\mathbf{\text{O}}$

Which ions do not appear in a net ionic equation? Why?

The allene molecule has the following Lewis structure:

Must all four hydrogen atoms lie in the same plane? If not, what is the spatial relationship among them? Why?

Many important compounds in the chemical industry are derivatives of ethylene $\mathbf{\left(}{\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{4}}\mathbf{\right)}$ . Two of them are acrylonitrile and methyl methacrylate.

Complete the Lewis structures for these molecules, showing all lone pairs. Give approximate values for bond angles a through f, and give the hybridization of all carbon atoms. In acrylonitrile and methyl methacrylate indicate which atoms in each molecule must lie in the same plane. How many s bonds and how many p bonds are there in acrylonitrile and methyl methacrylate?

Complete the following precipitation reactions with balanced molecular, total ionic, and net ionic equations:

$\begin{array}{l}\mathbf{\left(}\mathbf{a}\mathbf{\right)}{\mathbf{Hg}}_{\mathbf{2}}{\mathbf{\left(}{\mathbf{NO}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{2}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{+}\mathbf{KI}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{\to }\\ \mathbf{\left(}\mathbf{b}\mathbf{\right)}{\mathbf{FeSO}}_{\mathbf{4}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{+}\mathbf{Sr}{\mathbf{\left(}\mathbf{OH}\mathbf{\right)}}_{\mathbf{2}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{ }\mathbf{\to }\end{array}$

When each of the following pairs of aqueous solutions is mixed, does a precipitation reaction occur? If so, write balanced molecular, total ionic, and net ionic equations:

(a) Sodium nitrate + copper(II) sulfate 

(b) Ammonium bromide + silver nitrate

When each of the following pairs of aqueous solutions is mixed, does a precipitation reaction occur? If so, write balanced molecular, total ionic, and net ionic equations:

 (a) Potassium carbonate + barium hydroxide

 (b) Aluminium nitrate + sodium phosphate

When each of the following pairs of aqueous solutions is mixed, does a precipitation reaction occur? If so, write balanced molecular, total ionic, and net ionic equations.

(a) Potassium chloride + iron (III) nitrate 

(b) Ammonium sulfate + barium chloride

When each of the following pairs of aqueous solutions is mixed, does a precipitation reaction occur? If so, write balanced molecular, total ionic, and net ionic equations: 

(a) Sodium sulfide + nickel (II) sulfate 

(b) Lead (II) nitrate + potassium bromide

The precipitation reaction between 25.0 mL of a solution containing a cation (purple) and 35.0 mL of a solution containing an anion (green) is depicted below (with ions shown as spheres and solvent molecules omitted for clarity).

(a) Given the following choices of reactants, write balanced total ionic and net ionic equations that best represent the reaction: 

(1) KNO₃(aq) + CuCl₂(aq)

(2) NaClO₄(aq) + CaCl₂(aq) 

(3) Li2SO₄(aq) + AgNO₃(aq) 

(4) NH₄Br(aq) + Pb (CH₃COO)₂(aq) 

(b) If each sphere represents 2.5 x 10^-3 mol of ion, find the total number of ions present. 

(c) What is the mass of solid formed?

With ions shown as spheres and solvent molecules omitted for clarity, the circle (right) illustrates the solid formed when a solution containing ${\mathbf{\text{K}}}^{\mathbf{\text{+}}}{\mathbf{\text{,\hspace{0.17em}Mg}}}^{\mathbf{\text{2+}}}{\mathbf{\text{,\hspace{0.17em}Ag}}}^{\mathbf{\text{+}}}{\mathbf{\text{,\hspace{0.17em}or\hspace{0.17em}Pb}}}^{\mathbf{\text{2+}}}\mathbf{\left(}\mathbf{\text{blue}}\mathbf{\right)}$  is mixed with one containing  ${\mathbf{\text{ClO}}}_{\mathbf{\text{4}}}^{\mathbf{\text{-}}}{\mathbf{\text{,\hspace{0.17em}NO}}}_{\mathbf{\text{3}}}^{\mathbf{\text{-}}}{\mathbf{\text{,\hspace{0.17em}or\hspace{0.17em}SO}}}_{\mathbf{\text{4}}}^{\mathbf{\text{2-}}}\mathbf{\left(}\mathbf{\text{yellow}}\mathbf{\right)}\mathbf{\text{.}}$

(a) Identify the solid.

(b) Write a balanced net ionic equation for the reaction. 

(c) If each sphere represents ${\mathbf{\text{5.0×10}}}^{\mathbf{\text{4-}}}\mathbf{\text{\hspace{0.17em}mol}}$ of ion, what mass of product forms?

The mass percent of ${\mathbf{\text{Cl}}}^{\mathbf{\text{-}}}$  in a seawater sample is determined by titrating 25.00 mL of seawater with  ${\mathbf{\text{AgNO}}}_{\mathbf{\text{3}}}$  solution, causing a precipitation reaction. An indicator is used to detect the endpoint, which occurs when a free ${\mathbf{\text{Ag}}}^{\mathbf{\text{+}}}$   ion is present in the solution after all the ${\mathbf{\text{Cl}}}^{\mathbf{\text{-}}}$  has reacted. If 53.63 mL of 0.2970 M ${\mathbf{\text{AgNO}}}_{\mathbf{\text{3}}}$   is required to reach the endpoint, what is the mass percent of  ${\mathbf{\text{Cl}}}^{\mathbf{\text{-}}}$ in the seawater (d of seawater = 1.024 g/mL)?

Is the following a redox reaction? Explain

Describe how to determine the oxidation number of sulfur in

(a)  ${\mathrm{H}}_2\mathrm{S}$ and (b)${\mathbf{S}\mathbf{O}}_{\mathbf{3}}^{\mathbf{-}\mathbf{2}}$

An unknown amount of acid can often be determined by adding an excess of base and then “back-titrating” the excess. A 0.3471-g sample of a mixture of oxalic acid, which has two ionizable protons, and benzoic acid, which has one, is treated with 100.0 mL of 0.1000 M NaOH. The excess NaOH is titrated with 20.00 mL of 0.2000 M HCl. Find the mass % of benzoic acid.

Sodium hydroxide is used extensively in acid-base titrations because it is a strong, inexpensive base. A sodium hydroxide solution was standardized by titrating 25.00 mL of 0.1528 M standard hydrochloric acid. The initial buret reading of the sodium hydroxide was 2.24 mL, and the final reading was 39.21 mL. What was the molarity of the base solution?

An auto mechanic spills 88 mL of 2.6 M H₂SO₄ solution from a rebuilt auto battery. How many milliliters of 1.6 M NaHCO₃ must be poured on the spill to react completely with the sulfuric acid?

If 25.98 mL of a standard 0.1180 M KOH solution reacts with 52.50 mL of   solution, what is the molarity of the acid solution?

Why must every redox reaction involve an oxidizing agent and a reducing agent?

Is the total ionic equation the same as the net ionic equation when $\mathit{S}\mathit{r}{\mathbf{\left(}\mathbf{OH}\mathbf{\right)}}_{\mathbf{2}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}$ and ${\mathit{H}}_{\mathbf{2}}\mathit{S}{\mathit{O}}_{\mathbf{4}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}$ react? Explain.

The net ionic equation for the aqueous neutralization reaction between acetic acid and sodium hydroxide is different from that for the reaction between hydrochloric acid and sodium hydroxide. Explain by writing balanced net ionic equations.

Question: Zinc hydroxide is insoluble in water but dissolves when a nitric acid solution is added. Why? Write balanced total ionic and net ionic equations, showing nitric acid as it actually exists in water and the reaction as a proton-transfer process.

Question: State a general equation for a neutralization reaction.

Question: (a) Name three common weak acids. 

(b) Name one common weak base. 

(c) What is the major difference between a weak acid and a strong acid or between a weak base and a strong base, and what experiment would you perform to observe it?

 Do either of the following reactions go to completion? If so, what factor(s) cause(s) each to do so? 

1.   ${\mathrm{MgSO}}_3\left(\mathrm{s}\right)+2\mathrm{HCI}\left(\mathrm{aq}\right)\to {\mathrm{MgCI}}_2\left(\mathrm{aq}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}$
2.  $3\mathrm{Ba}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+2{\mathrm{H}}_3{\mathrm{PO}}_4\left(\mathrm{aq}\right)\to {\mathrm{Ba}}_3{\left({\mathrm{PO}}_4\right)}_2\left(\mathrm{s}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{I}\right)$

Que Complete the following acid-base reactions with balanced molecular, total ionic, and net ionic equations: 

(a) Potassium hydroxide(aq) + hydrobromic acid(aq) 

(b) Ammonia(aq) + hydrochloric acid(aq)

(a) Name three common strong acids. 

(b) Name three common strong bases. 

(c) What is a characteristic behavior of a strong acid or a strong base?

Complete the following acid-base reactions with balanced molecular, total ionic, and net ionic equations: 

(a) Cesium hydroxide(aq) + nitric acid(aq) 

(b) Calcium hydroxide(aq) + acetic acid(aq)

Limestone (calcium carbonate) is insoluble in water but dissolves when a hydrochloric acid solution is added. Write balanced total ionic and net ionic equations, showing hydrochloric acid as it actually exists in water and the reaction as a proton-transfer process.