Acids, Bases, and Salts: Chemistry Lecture Notes

Comprehensive vocabulary flashcards covering the definitions, classifications, preparations, and physical and chemical properties of acids.

Arrhenius Definition of an Acid

A substance that contains one or more hydrogen atoms and, when dissolved in water, ionizes and releases $H^+$ ions into the solution, forming hydronium ions ($H_3O^+$).

Hydronium Ion ($H_3O^+$)

The ion formed when a hydrogen ion ($H^+$) combines with a water molecule via the reaction $H^+ + H_2O \rightarrow H_3O^+$, because a bare $H^+$ ion is incapable of independent existence.

Natural Acid Sources

Common biological sources of organic acids: tomato and spinach contain oxalic acid; lemons and citrus fruits contain citric acid; apples contain malic acid; tamarind contains tartaric acid; curd contains lactic acid; vinegar contains acetic acid; and amla contains ascorbic acid.

Organic Acids

Acids derived from plants and animals that contain both carbon and hydrogen; they are weak acids that do not ionize completely in water and contain a mixture of both ions and molecules.

Inorganic Acids (Mineral Acids)

Acids obtained from minerals that generally do not contain carbon (with the exception of carbonic acid, $H_2CO_3$); they are typically strong acids that completely ionize in water to yield only ions.

Uses of Formic Acid ($HCOOH$)

An organic acid found in ant stings that is used commercially for tanning leather.

Uses of Sulfuric Acid ($H_2SO_4$)

A strong mineral acid utilized in car batteries, fertilizers, petroleum refining, and the production of artificial silk.

Uses of Phosphoric Acid ($H_3PO_4$)

A mineral acid utilized in anti-rust paint and fertilizers.

Basicity of an Acid

The number of replaceable $H^+$ ions present in a single molecule of an acid.

Monobasic Acid

An acid that produces only $1$ replaceable $H^+$ ion per molecule upon complete ionization (e.g., $HCl$, $HNO_3$, $CH_3COOH$, $HCOOH$) and forms only normal salts.

Dibasic Acid

An acid that produces $2$ replaceable $H^+$ ions per molecule upon complete ionization (e.g., $H_2SO_4$, $H_2CO_3$, $(COOH)_2$, $H_3PO_3$) and is capable of forming both acidic and normal salts.

Tribasic Acid

An acid that produces $3$ replaceable $H^+$ ions per molecule upon complete ionization (e.g., $H_3PO_4$) and is capable of forming both acidic and normal salts.

Strong Acid (Degree of Ionization)

An acid possessing a degree of ionization greater than $30\%$ that ionizes completely to produce a high concentration of $H^+$ ions, contains only ions in solution, and is a good electrical conductor.

Weak Acid (Degree of Ionization)

An acid possessing a degree of ionization less than $30\%$ that undergoes partial ionization to form a low concentration of $H^+$ ions, contains both ions and molecules in solution, and is a poor electrical conductor.

Hydracid

An acid that contains hydrogen and a non-metal element other than oxygen (e.g., $HCl$, $HF$, $HBr$).

Oxyacid

An acid composed of hydrogen, oxygen, and another non-metal element (e.g., $HNO_3$, $H_2SO_4$).

Preparation of Acids via Non-Metal Oxides

A synthesis method wherein an acidic non-metal oxide dissolves in water to produce an oxyacid (e.g., $SO_3 + H_2O \rightarrow H_2SO_4$ and $P_2O_5 + 3H_2O \rightarrow 2H_3PO_4$).

Direct Combination (Synthesis Reaction of Acids)

A preparation method where hydrogen gas combines directly with a non-metal to yield an acid, such as $H_2 + Cl_2 \rightarrow 2HCl$ or $H_2 + S \rightarrow H_2S$.

Oxidation of Non-metals (Acid Preparation)

A method of producing an acid by treating a non-metal with concentrated nitric acid ($HNO_3$), yielding an acid, water, and nitrogen dioxide gas (e.g., $S + 6HNO_3 \rightarrow H_2SO_4 + 2H_2O + 6NO_2$).

Acid Indicator Responses

Characteristic responses of chemical indicators in acidic media: blue litmus turns red, methyl orange turns red, phenolphthalein remains colorless, and turmeric paper remains yellow.

Effect of Acids on Skin

Corrosive chemical action that causes burns, producing yellow stains when exposed to $HNO_3$ or $HCl$, and black stains when exposed to concentrated $H_2SO_4$ due to charring.

Active Metals

Metals (such as $Fe$, $Zn$, $Ca$, $Mg$, $K$, $Al$, and $Na$) that readily displace hydrogen from dilute acids to yield a metal salt and hydrogen gas ($H_2$).

Reaction of Acids with Metal Carbonates and Bicarbonates

The reaction of an acid with a metallic carbonate or hydrogen carbonate producing a metal salt, carbon dioxide gas, and water: $\text{Acid} + \text{Metal Carbonate/Bicarbonate} \rightarrow \text{Metal Salt} + H_2O + CO_2$.

Reaction of Acids with Metallic Sulphites and Bisulphites

The chemical reaction yielding a metal salt, sulfur dioxide gas, and water: $\text{Acid} + \text{Metallic Sulphite/Bisulphite} \rightarrow \text{Salt} + SO_2 + H_2O$.

Reaction of Acids with Metallic Sulphides

The displacement reaction of a dilute acid with a metallic sulphide or bisulphide producing a salt and hydrogen sulphide gas ($H_2S$), such as $FeS + H_2SO_4 \rightarrow FeSO_4 + H_2S$.

Reaction of Concentrated $H_2SO_4$ with Metallic Chlorides

The reaction of concentrated sulfuric acid with a metal chloride to generate a metal sulfate and hydrogen chloride gas (e.g., $2NaCl + H_2SO_4 \rightarrow Na_2SO_4 + 2HCl$).

Laboratory Preparation of Nitric Acid ($HNO_3$)

The reaction between a metallic nitrate and concentrated sulfuric acid producing a salt and a more volatile acid: $2NaNO_3 + H_2SO_4 \rightarrow Na_2SO_4 + 2HNO_3$.

Neutralization Reaction

A chemical reaction between an acid and a base that produces a salt and water, such as $NaOH + HCl \rightarrow NaCl + H_2O$.