Reactions in Solutions and Electrochemistry Lecture Notes

These flashcards cover the key principles of aqueous solutions, electrolyte behavior, acid-base chemistry, titration, and the rules of oxidation-reduction reactions.

How is a solution defined in general chemistry?

A solution is a homogenous mixture of two or more substances where the solute is present in a small amount and the solvent is present in a larger quantity.

What is the difference between an aqueous and a nonaqueous solution?

In an aqueous solution, water is the solvent. In a nonaqueous solution, the solvent is a substance other than water, such as ethyl acetate used in nail polish removers.

What characterizes an electrolyte compared to a nonelectrolyte?

An electrolyte forms ions in solution and conducts electricity, whereas a nonelectrolyte does not form ions and the solution does not conduct electricity.

What happens when an ionic compound dissolves in water?

The ions dissociate, and each ion is surrounded by a shell of water molecules which stabilizes them and prevents cations and anions from recombining.

What are the specific exceptions of molecular compounds that ionize in water?

$NH_3(g)$ reacts with water to form $NH_4^+(aq)$ and $OH^-(aq)$, and $HCl(g)$ ionizes to form $H^+(aq)$ and $Cl^-(aq)$.

What is the difference between a strong and a weak electrolyte?

A strong electrolyte is almost completely ionized in aqueous solution and is a good conductor, while a weak electrolyte is only partially ionized and conducts electricity poorly.

What is the 'rule of thumb' for classifying organic substances as electrolytes or nonelectrolytes?

Ionic substances and carboxylic acids are electrolytes; alcohols, aldehydes, and ketones are nonelectrolytes.

What are the roles of potassium ($K^+$) and calcium ($Ca^{2+}$) in the human body?

Potassium (intracellular fluid) regulates heartbeat and muscle function. Calcium (extracellular fluid) carries electric charge in blood and 99% is stored in bones.

Define hyperkalemia and hypokalemia.

Hyperkalemia is an abnormal increase in potassium, and hypokalemia is an abnormal decrease in potassium.

What is a precipitation reaction?

A reaction where two solutions are mixed and an insoluble substance (solid) forms and separates from the solution.

What is an exchange (metathesis) reaction?

A reaction in which positive and negative ions in the reactants appear to exchange partners, represented by the general formula: $AX + BY \rightarrow AY + BX$.

What are spectator ions?

Ions that do not participate directly in the reaction and are present in the solution both before and after the reaction.

What was the calculated mass of $PbSO_4$ formed from the reaction of $1.25\,L$ of $0.050\,M$ lead (II) nitrate and $2.00\,L$ of $0.0250\,M$ sodium sulphate?

$15.2\,g\,PbSO_4$.

How did Arrhenius define an acid and a base?

An acid is a substance that produces $H^+$ ions when dissolved in water, and a base is a substance that produces $OH^-$ ions.

How did Bronsted-Lowry define an acid and a base?

An acid is a proton donor and a base is a proton acceptor.

List the seven major strong acids mentioned in the lecture.

Hydrochloric acid ($HCl$), Sulfuric acid ($H_2SO_4$), Hydrobromic acid ($HBr$), Nitric acid ($HNO_3$), Hydriodic acid ($HI$), Perchloric acid ($HClO_4$), and Chloric acid ($HClO_3$).

What is produced in a neutralization reaction between an acid and a metal hydroxide?

A salt and water.

What gas is formed when sodium sulfide ($Na_2S$) reacts with hydrochloric acid ($HCl$)?

Hydrogen sulfide gas ($H_2S(g)$).

What is the equivalence point (stoichiometric point) in a titration?

The point at which enough titrant has been added to react exactly with the analyte.

What is the difference between a primary standard and a secondary standard?

A primary standard is made by weighing a pure, stable solid ($H_2C_2O_4$, $Na_2CO_3$, $C_6H_5COOH$). A secondary standard requires titration to calibrate its concentration due to potential impurity or instability ($H_2SO_4$, $NH_3$, $NaOH$, $HCl$).

What is the formula for Molarity ($M$)?

$$M = \frac{\text{moles solute}}{\text{liters of solution}}$$

What is the formula used for dilution calculations?

$$M_1V_1 = M_2V_2$$

Define oxidation and reduction in a redox reaction.

Oxidation is the loss of electron(s) or an increase in oxidation state. Reduction is the gain of electron(s) or a decrease in oxidation state.

What is an oxidizing agent?

A substance that causes oxidation by accepting electrons, thereby becoming reduced itself.

According to the oxidation number rules, what is the oxidation number of an atom in its elemental state?

$0$ (zero).

What is the oxidation number of Hydrogen when bonded to a nonmetal vs. a metal?

$+1$ when bonded to a nonmetal and $-1$ when bonded to a metal or boron.

What is the oxidation number of Oxygen in peroxides ($O_2^{2-}$)?

$-1$.

In balancing redox reactions in basic solution using the half-reaction method, what extra step is required after balancing for $H^+$?

Add one $OH^-$ to both sides for every $H^+$ ion present, combine them to form water, and cancel out any waters appearing on both sides.