chemistry-english-note/contents/ions.tex

\section{Acids and bases ions}

\subsection{Hydrogen halides}

\subsubsection{Hydrofluoric acid}

\textbf{HF} (Hydrofluoric acid, Hydrogen fluoride)

\textbf{Properties:} Weak acid in aqueous solution (unlike other hydrogen halides), can dissolve glass.

\textbf{Reactions:}
\begin{itemize}
\item Etching glass: \ce{SiO2 + 4HF -> SiF4 ^ + 2H2O}
\item With calcium: \ce{Ca + 2HF -> CaF2 + H2 ^}
\item Formation of hexafluorosilicate: \ce{SiO2 + 6HF -> H2SiF6 + 2H2O}
\end{itemize}

\subsubsection{Hydrochloric acid}

\textbf{HCl} (Hydrochloric acid, Hydrogen chloride)

\textbf{Properties:} Strong acid, colorless gas, forms white fumes in moist air.

\textbf{Reactions:}
\begin{itemize}
\item Oxidation by manganese dioxide: \ce{MnO2 + 4HCl ->[heat] MnCl2 + Cl2 ^ + 2H2O}
\item With ammonia: \ce{NH3 + HCl -> NH4Cl} (white smoke)
\item Dissolving metals: \ce{Fe + 2HCl -> FeCl2 + H2 ^}
\item With permanganate: \ce{2KMnO4 + 16HCl -> 2KCl + 2MnCl2 + 5Cl2 ^ + 8H2O}
\end{itemize}

\subsubsection{Hydrobromic acid}

\textbf{HBr} (Hydrobromic acid, Hydrogen bromide)

\textbf{Properties:} Strong acid, stronger reducing agent than HCl.

\textbf{Reactions:}
\begin{itemize}
\item Oxidation by sulfuric acid: \ce{2HBr + H2SO4 -> Br2 + SO2 + 2H2O}
\item With silver nitrate: \ce{HBr + AgNO3 -> AgBr v + HNO3} (pale yellow precipitate)
\end{itemize}

\subsubsection{Hydroiodic acid}

\textbf{HI} (Hydroiodic acid, Hydrogen iodide)

\textbf{Properties:} Strong acid, strongest reducing agent among hydrogen halides.

\textbf{Reactions:}
\begin{itemize}
\item Oxidation by sulfuric acid: \ce{8HI + H2SO4 -> 4I2 + H2S + 4H2O}
\item Reduction of Fe(III): \ce{2Fe^3+ + 2I- -> 2Fe^2+ + I2}
\item With chlorine: \ce{2HI + Cl2 -> 2HCl + I2}
\end{itemize}

\subsection{Oxyacid}

\subsubsection{Nitrogen oxyacids}

\textbf{HNO$_2$} (Nitrous acid)

\textbf{Structure:} \chemfig{H-O-N=O}

\textbf{Valence:} N is +3

\textbf{Properties:} Weak acid, unstable, exists only in solution.

\textbf{Reactions:}
\begin{itemize}
\item Decomposition: \ce{3HNO2 -> HNO3 + 2NO ^ + H2O}
\item Oxidation of iodide: \ce{2HNO2 + 2HI -> I2 + 2NO ^ + 2H2O}
\item Reduction by reducing agents: \ce{2HNO2 + 2HI -> 2NO ^ + I2 + 2H2O}
\end{itemize}

\textbf{HNO$_3$} (Nitric acid)

\textbf{Structure:} \chemfig{H-O-[:30]N(=[2]O)(=[:-30]O)}

\textbf{Valence:} N is +5

\textbf{Properties:} Strong acid, strong oxidizing agent.

\textbf{Reactions:}
\begin{itemize}
\item With copper: \ce{3Cu + 8HNO3(dilute) -> 3Cu(NO3)2 + 2NO ^ + 4H2O}
\item Concentrated with copper: \ce{Cu + 4HNO3(conc.) -> Cu(NO3)2 + 2NO2 ^ + 2H2O}
\item Nitration reaction: \ce{C6H6 + HNO3 ->[H2SO4] C6H5NO2 + H2O}
\item With phosphorus: \ce{P4 + 20HNO3 -> 4H3PO4 + 20NO2 ^ + 4H2O}
\item Passivation of iron: \ce{Fe + 6HNO3(conc.) -> Fe^3+ (passive layer)}
\end{itemize}

\subsubsection{Sulfur oxyacids}

\textbf{H$_2$SO$_3$} (Sulfurous acid)

\textbf{Structure:} \chemfig{HO-[:30]S(=[2]O)(-[:-30]OH)}

\textbf{Valence:} S is +4

\textbf{Properties:} Weak acid, exists only in solution, reducing agent.

\textbf{Reactions:}
\begin{itemize}
\item Oxidation by oxygen: \ce{2H2SO3 + O2 -> 2H2SO4}
\item Reduction by hydrogen sulfide: \ce{H2SO3 + 2H2S -> 3S v + 3H2O}
\item With bromine: \ce{H2SO3 + Br2 + H2O -> H2SO4 + 2HBr}
\end{itemize}

\textbf{H$_2$SO$_4$} (Sulfuric acid)

\textbf{Structure:} \chemfig{S(=[2]O)(=[:200]O)(<[:300]OH)(<:[:-20]OH)}

\textbf{Valence:} S is +6

\textbf{Properties:} Strong acid, strong dehydrating agent, strong oxidizing agent (concentrated).

\textbf{Reactions:}
\begin{itemize}
\item With carbon (dehydration): \ce{C12H22O11 ->[H2SO4(conc.)] 12C + 11H2O}
\item Hot concentrated with copper: \ce{Cu + 2H2SO4(conc.) ->[heat] CuSO4 + SO2 ^ + 2H2O}
\item With NaCl (making HCl): \ce{NaCl + H2SO4 ->[heat] NaHSO4 + HCl ^}
\item Esterification: \ce{CH3COOH + C2H5OH <=>[H2SO4] CH3COOC2H5 + H2O}
\end{itemize}

\subsubsection{Phosphorus oxyacids}

\textbf{H$_3$PO$_3$} (Phosphorous acid)

\textbf{Structure:} \chemfig{H-[:30]P(=[2]O)(<[:300]OH)(<:[:-20]OH)}

\textbf{Valence:} P is +3

\textbf{Properties:} Dibasic acid (only 2 acidic H), reducing agent.

\textbf{Reactions:}
\begin{itemize}
\item Reduction of silver nitrate: \ce{H3PO3 + 2AgNO3 + H2O -> H3PO4 + 2Ag v + 2HNO3}
\item Disproportionation: \ce{4H3PO3 ->[heat] 3H3PO4 + PH3 ^}
\end{itemize}

\textbf{H$_3$PO$_4$} (Phosphoric acid)

\textbf{Structure:} \chemfig{HO-[:30]P(=[2]O)(<[:300]OH)(<:[:-20]OH)}

\textbf{Valence:} P is +5

\textbf{Properties:} Weak tribasic acid, non-oxidizing.

\textbf{Reactions:}
\begin{itemize}
\item Dehydration to pyrophosphoric acid: \ce{2H3PO4 ->[heat] H4P2O7 + H2O}
\item With ammonia: \ce{H3PO4 + NH3 -> NH4H2PO4}
\item Esterification: \ce{H3PO4 + 3C2H5OH -> (C2H5O)3PO + 3H2O}
\end{itemize}

\subsubsection{Chlorine oxyacids}

\textbf{HClO} (Hypochlorous acid)

\textbf{Structure:} \chemfig{H-O-Cl}

\textbf{Valence:} Cl is +1

\textbf{Properties:} Very weak acid, strong oxidizing agent, unstable.

\textbf{Reactions:}
\begin{itemize}
\item Disproportionation: \ce{3HClO -> HClO3 + 2HCl}
\item Oxidation: \ce{HClO + H2S -> HCl + S v + H2O}
\item Bleaching: \ce{HClO + [dye] -> [oxidized dye] (colorless)}
\end{itemize}

\textbf{HClO$_2$} (Chlorous acid)

\textbf{Structure:} \chemfig{H-O-[:30]Cl(=[2]O)}

\textbf{Valence:} Cl is +3

\textbf{Properties:} Weak acid, unstable, exists only in solution.

\textbf{HClO$_3$} (Chloric acid)

\textbf{Structure:} \chemfig{H-O-[:30]Cl(=[2]O)(=[:-30]O)}

\textbf{Valence:} Cl is +5

\textbf{Properties:} Strong acid, strong oxidizing agent.

\textbf{Reactions:}
\begin{itemize}
\item Oxidation of sulfur: \ce{3S + 6HClO3 -> 3H2SO4 + 3Cl2 ^}
\item Decomposition: \ce{8HClO3 -> 4Cl2 ^ + 6O2 ^ + 4H2O}
\end{itemize}

\textbf{HClO$_4$} (Perchloric acid)

\textbf{Structure:} \chemfig{HO-[:30]Cl(=[2]O)(=[:300]O)(=[:-20]O)}

\textbf{Valence:} Cl is +7

\textbf{Properties:} Very strong acid, strongest common acid, powerful oxidizing agent when hot/concentrated.

\textbf{Reactions:}
\begin{itemize}
\item Oxidation of organic compounds: \ce{C6H12O6 + 24HClO4 ->[heat] 6CO2 ^ + 12Cl2 ^ + 18H2O}
\item With metals: \ce{Mg + 2HClO4 -> Mg(ClO4)2 + H2 ^}
\end{itemize}

\subsubsection{Carbon oxyacids}

\textbf{H$_2$CO$_3$} (Carbonic acid)

\textbf{Structure:} \chemfig{HO-[:30]C(=[2]O)(-[:-30]OH)}

\textbf{Valence:} C is +4

\textbf{Properties:} Weak acid, unstable, exists in equilibrium with CO$_2$ and H$_2$O.

\textbf{Reactions:}
\begin{itemize}
\item Decomposition: \ce{H2CO3 <=> CO2 ^ + H2O}
\item With ammonia: \ce{H2CO3 + 2NH3 -> (NH4)2CO3}
\item Formation: \ce{CO2 + H2O <=> H2CO3}
\end{itemize}

\subsubsection{Bromine and iodine oxyacids}

\textbf{HBrO} (Hypobromous acid)

\textbf{Structure:} \chemfig{H-O-Br}

\textbf{Valence:} Br is +1

\textbf{HBrO$_3$} (Bromic acid)

\textbf{Structure:} \chemfig{H-O-[:30]Br(=[2]O)(-[:-30]O)}

\textbf{Valence:} Br is +5

\textbf{HIO$_3$} (Iodic acid)

\textbf{Structure:} \chemfig{H-O-[:30]I(=[2]O)(-[:-30]O)}

\textbf{Valence:} I is +5

\textbf{Reactions:}
\begin{itemize}
\item Oxidation: \ce{5HI + HIO3 -> 3I2 + 3H2O}
\item With sulfur dioxide: \ce{HIO3 + 3H2SO3 -> HI + 3H2SO4}
\end{itemize}

\textbf{H$_5$IO$_6$} (Periodic acid)

\textbf{Structure:} \chemfig{I(=[2]O)(<:[:30]OH)(<[:-30]OH)(<:[:150]OH)(<[:210]OH)(-[:270]OH)}

\textbf{Valence:} I is +7

\textbf{Reactions:}
\begin{itemize}
\item Oxidative cleavage of diols: Used to cleave vicinal diols (glycols) to aldehydes or ketones
\end{itemize}

\subsection{Bases from metal oxides}

\subsubsection{Alkali metal hydroxides}

\textbf{NaOH} (Sodium hydroxide, Caustic soda, Lye)

\textbf{Valence:} Na is +1

\textbf{Properties:} Strong base, deliquescent, corrosive.

\textbf{Reactions:}
\begin{itemize}
\item With aluminum (amphoteric): \ce{2Al + 2NaOH + 2H2O -> 2NaAlO2 + 3H2 ^}
\item With silicon dioxide: \ce{SiO2 + 2NaOH ->[heat] Na2SiO3 + H2O}
\item Saponification of esters: \ce{CH3COOC2H5 + NaOH -> CH3COONa + C2H5OH}
\item With chlorine (disproportionation): \ce{Cl2 + 2NaOH -> NaCl + NaClO + H2O}
\item With sulfur: \ce{3S + 6NaOH ->[heat] 2Na2S + Na2SO3 + 3H2O}
\end{itemize}

\textbf{KOH} (Potassium hydroxide, Caustic potash)

\textbf{Valence:} K is +1

\textbf{Properties:} Strong base, more hygroscopic than NaOH.

\textbf{Reactions:}
\begin{itemize}
\item With CO$_2$: \ce{2KOH + CO2 -> K2CO3 + H2O}
\item Excess CO$_2$: \ce{K2CO3 + CO2 + H2O -> 2KHCO3}
\item With haloalkanes (elimination): \ce{C2H5Br + KOH ->[alcohol] C2H4 ^ + KBr + H2O}
\end{itemize}

\textbf{LiOH} (Lithium hydroxide)

\textbf{Valence:} Li is +1

\textbf{Properties:} Strong base, used in CO$_2$ scrubbers.

\textbf{Reactions:}
\begin{itemize}
\item CO$_2$ absorption: \ce{2LiOH + CO2 -> Li2CO3 + H2O}
\end{itemize}

\subsubsection{Alkaline earth metal hydroxides}

\textbf{Ca(OH)$_2$} (Calcium hydroxide, Slaked lime, Hydrated lime)

\textbf{Valence:} Ca is +2

\textbf{Properties:} Moderately strong base, sparingly soluble in water (lime water).

\textbf{Reactions:}
\begin{itemize}
\item With CO$_2$ (limewater test): \ce{Ca(OH)2 + CO2 -> CaCO3 v + H2O}
\item Excess CO$_2$: \ce{CaCO3 + CO2 + H2O -> Ca(HCO3)2} (soluble)
\item With chlorine: \ce{2Ca(OH)2 + 2Cl2 -> CaCl2 + Ca(ClO)2 + 2H2O}
\item Preparation from quicklime: \ce{CaO + H2O -> Ca(OH)2} (exothermic)
\end{itemize}

\textbf{Mg(OH)$_2$} (Magnesium hydroxide, Milk of magnesia)

\textbf{Valence:} Mg is +2

\textbf{Properties:} Weak base, very sparingly soluble, antacid.

\textbf{Reactions:}
\begin{itemize}
\item Decomposition: \ce{Mg(OH)2 ->[heat] MgO + H2O}
\item With acids (antacid action): \ce{Mg(OH)2 + 2HCl -> MgCl2 + 2H2O}
\end{itemize}

\textbf{Ba(OH)$_2$} (Barium hydroxide)

\textbf{Valence:} Ba is +2

\textbf{Properties:} Strong base, more soluble than Ca(OH)$_2$.

\textbf{Reactions:}
\begin{itemize}
\item With sulfuric acid: \ce{Ba(OH)2 + H2SO4 -> BaSO4 v + 2H2O}
\item With ammonium salts (endothermic): \ce{Ba(OH)2.8H2O + 2NH4Cl -> BaCl2 + 2NH3 ^ + 10H2O}
\end{itemize}

\subsubsection{Ammonia and related bases}

\textbf{NH$_3$} (Ammonia)

\textbf{Structure:} \chemfig{N(-[:90]H)(-[:210]H)(-[:330]H)}

\textbf{Valence:} N is -3

\textbf{Properties:} Weak base, pungent gas, very soluble in water.

\textbf{Reactions:}
\begin{itemize}
\item Complex formation with Cu$^{2+}$: \ce{Cu^2+ + 4NH3 -> [Cu(NH3)4]^2+} (deep blue)
\item With HCl: \ce{NH3 + HCl -> NH4Cl} (white smoke)
\item Haber process: \ce{N2 + 3H2 <=>[Fe catalyst][high T, P] 2NH3}
\item Oxidation by oxygen: \ce{4NH3 + 5O2 ->[Pt catalyst] 4NO + 6H2O} (Ostwald process)
\item With chlorine: \ce{2NH3 + 3Cl2 -> N2 + 6HCl}
\item Reduction of CuO: \ce{3CuO + 2NH3 ->[heat] 3Cu + N2 + 3H2O}
\end{itemize}

\textbf{NH$_4$OH} (Ammonium hydroxide)

\textbf{Formula:} NH$_4^+$ and OH$^-$ ions in aqueous solution

\textbf{Valence:} N is -3

\textbf{Properties:} Aqueous ammonia solution, weak base.

\textbf{Reactions:}
\begin{itemize}
\item Precipitation of metal hydroxides: \ce{Fe^3+ + 3NH4OH -> Fe(OH)3 v + 3NH4+}
\item With excess ammonia (complex formation): \ce{Zn(OH)2 + 4NH3 -> [Zn(NH3)4]^2+ + 2OH-}
\end{itemize}

\subsubsection{Transition metal hydroxides}

\textbf{Fe(OH)$_2$} (Iron(II) hydroxide, Ferrous hydroxide)

\textbf{Valence:} Fe is +2

\textbf{Properties:} Weak base, white-green solid, easily oxidized.

\textbf{Reactions:}
\begin{itemize}
\item Oxidation: \ce{4Fe(OH)2 + O2 + 2H2O -> 4Fe(OH)3} (turns brown)
\item Decomposition: \ce{Fe(OH)2 ->[heat] FeO + H2O}
\end{itemize}

\textbf{Fe(OH)$_3$} (Iron(III) hydroxide, Ferric hydroxide)

\textbf{Valence:} Fe is +3

\textbf{Properties:} Very weak base, brown precipitate.

\textbf{Reactions:}
\begin{itemize}
\item Decomposition: \ce{2Fe(OH)3 ->[heat] Fe2O3 + 3H2O}
\end{itemize}

\textbf{Al(OH)$_3$} (Aluminum hydroxide)

\textbf{Valence:} Al is +3

\textbf{Properties:} Amphoteric, white precipitate, antacid.

\textbf{Reactions:}
\begin{itemize}
\item With acid: \ce{Al(OH)3 + 3HCl -> AlCl3 + 3H2O}
\item With base: \ce{Al(OH)3 + NaOH -> NaAlO2 + 2H2O}
\item Decomposition: \ce{2Al(OH)3 ->[heat] Al2O3 + 3H2O}
\end{itemize}

\textbf{Cu(OH)$_2$} (Copper(II) hydroxide, Cupric hydroxide)

\textbf{Valence:} Cu is +2

\textbf{Properties:} Weak base, blue precipitate.

\textbf{Reactions:}
\begin{itemize}
\item Decomposition: \ce{Cu(OH)2 ->[heat] CuO + H2O}
\item With ammonia: \ce{Cu(OH)2 + 4NH3 -> [Cu(NH3)4]^2+ + 2OH-} (deep blue solution)
\item With tartaric acid (Fehling's reagent): Forms copper tartrate complex
\end{itemize}