Thermochemistry and Acids/Bases Review

Flashcards based on Thermochemistry and Acids/Bases Lecture Notes

Thermochemistry (or Thermodynamics)

The study of heat, work, energy, and temperature changes that occur during chemical reactions.

Energy

The capacity to produce heat or do work.

Potential Energy

Energy stored in chemical bonds.

Kinetic Energy

Energy due to motion of molecules.

Law of Conservation of Energy (1st Law of Thermodynamics)

The energy of the universe is constant; it is neither created nor destroyed.

Temperature

The measure of the average kinetic energy of the particles in a substance.

Heat (q)

The energy that is transferred between two objects by collisions between the particles.

System

What we are interested in, usually the reactants and products.

Surroundings

Everything else, including the reaction container.

Exothermic

Heat/Energy flows out of the system; q is negative.

Endothermic

Heat/Energy flows into the system; q is positive.

Joule (J)

The SI unit of heat and energy.

Calorie (cal)

The amount of heat needed to raise the temperature of 1g of pure water by 1°C; 1 cal = 4.184 J.

Specific heat capacity (C)

The amount of heat needed to raise the temperature of one gram of a substance by 1°C.

Potential Energy Diagrams (PEDs)

Diagrams that help us see how energy changes during a chemical reaction.

Activation Energy Source

Energy from normal molecular collisions, heat/sparks, or light.

Enthalpy of Reaction (∆H)

The enthalpy of the products minus the enthalpy of the reactants: ∆Hrxn = Hproducts − Hreactants

Acid

Substance that produces H+ ions when dissolved in water.

Base

Substance that produces OH- ions in water.

Acid-Base Reaction

In an acid-base reaction, the acid donates a proton (H+) to the base.

Neutralization Reaction

When solutions of an acid and a base are combined, the products are a salt and water.

Strong Acids and Bases

Acids and bases that dissociate completely into ions.

Weak Acids/Bases

Acids and bases that dissociate only a little, leaving mostly intact molecules.

Strong acids

Completely dissociated in water.

Weak acids

Only dissociate partially in water.

pH

The negative base-10 logarithm of a solution’s concentration of hydronium ion. pH = -log [H3O+] or pH = -log [H+]