CHEM 1405 Concept Review: Acids and Bases

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Arrhenius Acid: Any substance that produces H⁺ ions when dissolved in water.

Arrhenius Base: Any substance that produces OH^- ions when dissolved in water.

Bronsted-Lowry Acid: A substance that donates a proton (H⁺) in a chemical reaction.

Bronsted-Lowry Base: A substance that accepts a proton (H⁺) in a chemical reaction

Bronsted-Lowry Acid-Base/Conjugate Acid-Conjugate Base Reactions

The conjugate acid and the conjugate base are the acid and base for the REVERSE reaction.

Note: The acid and base are ALWAYS your reactants. The conjugate acid and base are ALWAYS products.

Naming Acids

Ion Type	Generic Ion Name	Generic Acid Name	Example Ion	Example Acid
Polyatomic	(root)-ate	(root)-ic acid	Chlorate: ClO₃^-	Chloric acid: HClO₃
Polyatomic	Per-(root)-ate	Per-(root)-ic acid	Perchlorate: ClO₄^-	Perchloric acid: HClO₄
Polyatomic	(root)-ite	(root)-ous acid	Chlorite: ClO₂^-	Chlorous acid: HClO₂
Polyatomic	Hypo-(root)-ite	Hypo-(root)-ous acid	Hypochlorite: ClO^-	Hypochlorous acid: HClO
Monatomic	(root)-ide	Hydro-(root)-ic acid	Chloride: Cl^-	Hydrochloric acid: HCl

Important Note: The “root” for sulfate (SO₄^2-) and sulfide (S^2-) changes from “sulf-“ to “sulfur” and the “root” for phosphate (PO₄^3-) changes from “phosph-“ to “phosphor-“ in acid naming.

Naming bases is the same as naming ionic compounds. The strong bases are simply soluble metal hydroxides.

Strong Acids/Bases: Acids or bases that completely ionize (i.e.-dissociate) in water.

Example: $LaTeX: HCl\left(aq\right)\longrightarrow H^+\left(aq\right)+Cl^-\left(aq\right)$ $HCl\left(aq\right)\longrightarrow H^+\left(aq\right)+Cl^-\left(aq\right)$ Example: $LaTeX: NaOH\left(s\right)\longrightarrow Na^+\left(aq\right)+OH^-\left(aq\right)$ $NaOH\left(s\right)\longrightarrow Na^+\left(aq\right)+OH^-\left(aq\right)$

Weak Acids/Bases: Acids or bases that only slightly ionize (i.e.-dissociate) in water

Example: $LaTeX: HCN\left(aq\right)\longleftrightarrow H^+\left(aq\right)+CN^-\left(aq\right)$ $HCN\left(aq\right)\longleftrightarrow H^+\left(aq\right)+CN^-\left(aq\right)$ Example: $LaTeX: NH_3\left(aq\right)+H_2O\left(l\right)\longleftrightarrow NH_4^+\left(aq\right)+OH^-\left(aq\right)$ $NH_3\left(aq\right)+H_2O\left(l\right)\longleftrightarrow NH_4^+\left(aq\right)+OH^-\left(aq\right)$

Strong Acids and Bases (Memorize this Table)

Strong Acids

Strong Bases

HCl: Hydrochloric Acid

HBr: Hydrobromic Acid

HI: Hydroiodic Acid

HNO₃: Nitric Acid

HClO₄: Perchloric Acid

HClO₃: Chloric Acid

H₂SO₄: Sulfuric Acid

LiOH: Lithium hydroxide

NaOH: Sodium hydroxide

KOH: Potassium hydroxide

RbOH: Rubidium hydroxide

CsOH: Cesium Hydroxide

Ca(OH)₂:Calcium hydroxide

Sr(OH)₂: Strontium hydroxide

Ba(OH)₂: Barium hydroxide

The auto-ionization equilibrium of water:

$LaTeX: H_2O\left(l\right)+H_2O\left(l\right)\:\longrightarrow\:H_3O^+\left(aq\right)+OH^-\left(aq\right)$ $H_2O\left(l\right)+H_2O\left(l\right)\:\longrightarrow\:H_3O^+\left(aq\right)+OH^-\left(aq\right)$

The ion product constant of water K_w, can be expressed in the following relationship:

$LaTeX: K_w=\left[H_3O^+\right]\left[OH^-\right]$ $K_w=\left[H_3O^+\right]\left[OH^-\right]$ , where $LaTeX: K_w=1.0\times10^{-14}$ $K_w=1.0\times10^{-14}$ (at 25˚C)

Acid-Base Comparison

$LaTeX: If\:\left[H_3O^+\right]>\left[OH^-\right]$ $If\:\left[H_3O^+\right]>\left[OH^-\right]$ , the solution is acidic.

$LaTeX: If\:\left[H_3O^+\right]=\left[OH^-\right]$ $If\:\left[H_3O^+\right]=\left[OH^-\right]$ , the solution is neutral.

$LaTeX: If\:\left[H_3O^+\right]<\left[OH^-\right]$ $If\:\left[H_3O^+\right]<\left[OH^-\right]$ , the solution is basic.

(Note: H₃O⁺ and H⁺ are often used interchangeably in acid-base chemistry)

pH and Calculations with pH

In pH, the “p” means “power of”, therefore the pH is the “power of hydrogen”, which refers to the magnitude of the negative exponent of the hydrogen ion concentration, [H⁺]. Mathematically, we determine the “power of hydrogen” by taking the negative logarithm of the hydrogen ion concentration, therefore mathematically “p” means “-log”. Thus, we have the following relationship:

$LaTeX: pH=-\log\left[H_3O^+\right]\:\:\:\:\:\:or\:\:\:\:\:\:pH=-\log\left[H^+\right]$ $pH=-\log\left[H_3O^+\right]\:\:\:\:\:\:or\:\:\:\:\:\:pH=-\log\left[H^+\right]$

To “undo” a logarithm and go from pH back to the concentration of H₃O⁺/H⁺, take the inverse log of “-pH”:

$LaTeX: \left[H_3O^+\right]=10^{-pH}\:\:\:\:\:\:\:\:\:or\:\:\:\:\:\:\:\:\:\left[H^+\right]=10^{-pH}$ $\left[H_3O^+\right]=10^{-pH}\:\:\:\:\:\:\:\:\:or\:\:\:\:\:\:\:\:\:\left[H^+\right]=10^{-pH}$

1406 Ch 10 img 2-1.jpg

Reactions with Acids

Acids and Metals: Reaction of an acid with a metal will produce a salt and hydrogen gas.

$LaTeX: Example\:\:\:\:\:\:\:\:\:\:Mg\left(s\right)+2HCl\left(aq\right)\:\longrightarrow\:MgCl_2\left(aq\right)+H_2\left(g\right)$ $Example\:\:\:\:\:\:\:\:\:\:Mg\left(s\right)+2HCl\left(aq\right)\:\longrightarrow\:MgCl_2\left(aq\right)+H_2\left(g\right)$

Acids and Carbonates or Bicarbonates: Acids will react with carbonates and bicarbonates to form a salt, CO₂, and H₂O

$LaTeX: Example\:\:\:\:\:\:\:\:\:\:2HCl\left(aq\right)+Na_2CO_3\left(aq\right)\:\longrightarrow\:CO_2\left(g\right)+H_2O\left(l\right)+2NaCl\left(aq\right)\:\:\:\:\:\:\:\:\left(carbonate\right)$ $Example\:\:\:\:\:\:\:\:\:\:2HCl\left(aq\right)+Na_2CO_3\left(aq\right)\:\longrightarrow\:CO_2\left(g\right)+H_2O\left(l\right)+2NaCl\left(aq\right)\:\:\:\:\:\:\:\:\left(carbonate\right)$ $LaTeX: Example\:\:\:\:\:\:\:\:\:\:\:HBr\left(aq\right)+NaHCO_3\left(aq\right)\:\longrightarrow\:CO_2\left(g\right)+H_2O\left(l\right)+NaBr\left(aq\right)\:\:\:\:\:\:\:\:\:\left(bicarbonate\right)$ $Example\:\:\:\:\:\:\:\:\:\:\:HBr\left(aq\right)+NaHCO_3\left(aq\right)\:\longrightarrow\:CO_2\left(g\right)+H_2O\left(l\right)+NaBr\left(aq\right)\:\:\:\:\:\:\:\:\:\left(bicarbonate\right)$

Neutralization: A double replacement reaction between an acid and a base that produces a salt and water.

$LaTeX: Example\:\:\:\:\:\:\:\:\:\:\:\:HI\left(aq\right)+NaOH\left(aq\right)\:\longrightarrow\:NaI\left(aq\right)+H_2O\left(l\right)$ $Example\:\:\:\:\:\:\:\:\:\:\:\:HI\left(aq\right)+NaOH\left(aq\right)\:\longrightarrow\:NaI\left(aq\right)+H_2O\left(l\right)$

Buffer: A solution containing both a weak acid and its conjugate base, which resists changes to pH from added acid/base.