Introduction to Chemical Reactions, Thermodynamics, Electrochemistry, and Organic Chemistry

Practice flashcards reviewing chemical reactions, thermodynamics, equilibrium, acids and bases, electrochemistry, and organic chemistry concepts.

What is a chemical reaction?

A change resulting from a collision between atoms or molecules.

What is the Law of Conservation of Mass?

It states that mass is neither created nor destroyed during a chemical reaction, meaning the total mass of the starting materials (reactants) always equals the total mass of the new substances (products).

What are the four observations that indicate a chemical reaction has occurred?

1. A change of color, 2. Formation of gas, 3. The formation of a precipitate, 4. The release or absorption of energy (often as light or heat).

What does the arrow ($\rightarrow$) signify in a chemical equation?

It means "yields" and indicates that the substances react to form each other.

What are the three guidelines for balancing a chemical equation?

1) Only the coefficients, not the subscripts, may be adjusted; 2) Balance the element with the largest subscript first; 3) In an equation involving a pure element and one or more compounds, balance the pure element last.

What is a combination reaction?

A chemical reaction in which two or more substances combine to form a new substance, represented as $A + B \rightarrow AB$.

What is a decomposition reaction?

A chemical reaction in which a compound breaks down, or decomposes, to create different substances, represented as $AB \rightarrow A + B$.

What is a single-displacement reaction?

A chemical reaction in which an element in a compound is replaced by another element (also called a substitution reaction), represented as $A + BC \rightarrow B + AC$.

What chemical equation represents the thermite reaction?

$$2Al + Fe_2O_3 \rightarrow 2Fe + Al_2O_3$$

What is a double-displacement reaction?

A chemical reaction in which two compounds exchange atoms or ions, represented as $AB + CD \rightarrow AD + CB$.

What does the First Law of Thermodynamics state regarding chemical reactions?

Energy gained or lost by the system equals the energy lost or gained by the surroundings.

How do exothermic and endothermic reactions differ?

An exothermic reaction releases thermal energy to the surroundings, whereas an endothermic reaction causes thermal energy to be absorbed and stored in the chemical bonds of the products.

What does the Second Law of Thermodynamics state regarding chemical reactions?

Every chemical reaction must cause a decrease in usable energy and an increase in entropy (disorder).

What is activation energy?

The kinetic energy necessary for molecules to chemically react.

What is a catalyst?

A substance that alters the rate of a chemical reaction without it being permanently changed in the reaction.

What is Le Chatelier's principle?

States that when a system at equilibrium is disturbed, the system will react to at least partially offset that disturbance.

How does an increase in pressure affect a gas-phase reaction at equilibrium?

Equilibrium will shift toward the side with the fewer number of gas molecules.

What is an acid and a base according to the transcript?

An acid is any substance that produces hydrogen cations ($H^+$) when dissolved in an aqueous solution. A base is any substance that produces hydroxide anions ($OH^-$) in an aqueous solution.

What is an oxonium (hydronium) ion and how is it formed?

Symbolized as $H_3O^+$ ion, it is formed by $H^+$ ions attaching themselves to water in an aqueous solution.

What concentration of $H_3O^+$ defines a neutral solution?

A solution with $[H_3O^+]$ equal to $1 \times 10^{-7}\,mol/L$.

What is a buffer?

Any solution that resists changes in pH because it contains a weak acid and one of its basic salts or a weak base and one of its acidic salts.

What are oxidation and reduction?

Oxidation is the process in which an atom loses electrons in a reaction; reduction is the process in which an atom gains electrons.

What happens at the anode and cathode of an electrochemical cell?

Oxidation occurs at the anode (losing electrons), and reduction occurs at the cathode (gaining electrons).

What is the distinction between a voltaic cell, a storage cell, and a fuel cell?

A voltaic cell is a nonrechargeable cell producing electricity; a storage cell can be recharged with electricity from an outside current source; a fuel cell has its reactants continually replenished from an outside source.

How are alkanes, alkenes, and alkynes defined?

An alkane is a hydrocarbon having only single bonds between carbon atoms; an alkene contains one or more double bonds; an alkyne contains one or more triple bonds.

What is glucose and what is its molecular formula?

Glucose is an important six-carbon sugar found in both animals and plants, with the molecular formula $C_6H_{12}O_6$.

How do starch, glycogen, and cellulose function differently?

Starch is a group of polysaccharides used by plants for food storage; glycogen is used by animals and people for food storage; cellulose forms the cell walls of plant cells.