Chemistry - 2nd Quarter: Exam

Molar Mass

Numerically equal to the atomic mass of the element, the molecular mass of a covalent compound, or the formula mass of an ionic compound.

Avogadro’s Number (6.022 x 10²³

When solving problems dealing with the number of objects (atoms or molecules) present in a given number of moles of a substance _____ becomes part of the conversion factor used to relate the number of objcets present to the number of moles present

Molecules

is the particle unit for covalent compounds.

Formula Units

is the particle unit for ionic compounds

Mole

a term used to refer to the number of particles of a substance. (atoms, ions, molecules, or formula units)

Chemical Reactions

Shows the identity of the reactants and products and the relative amounts of these substances consumed or produced in a chemical reaction.

Synthesis or Combination

• Two or more substances join and form one single substance.

• A + B → AB

Decomposition or Analysis

One compound breaks down into two products.

AB → A + B

Single Replacement or Substitution

atoms of an element swap with atoms of a second element in a compound
AB + C → AC + B

Double displacement or Metatesis

positive ions exchange between two compounds.
AB + CD → AC + BD

Combustion

a reaction between any combustible substance and an oxidizer takes place to form an oxidized product
Fuel + O2 → CO2 + H2O

Percent composition

is the percentage by mass of each element in a compound, showing how much of the compound’s total mass comes from each element.

CHEMICAL FORMULA

Is a chemical symbol of a substance used to illustrate the composition of a compound.

Molecular Formula

shows the exact number of atoms comprising a compound.

Empirical Formula

shows the lowest whole number ratio of atoms in a compound.

excess reactant 

The reactant left after the reaction or the reactant which is not totally consumed.

Limiting reactant

The reactant that is consumed first.

Percent Yield

The efficient of a chemical reaction can be determined by the percent yield which is the ratio of the actual yield to the theoretical yield multiplied by 100:

theoretical yield

The maximum amount of product that could be formed from the given amounts of reactants.

Actual yield

is the quantity of a product that is obtained from a chemical reaction.

STOICHIOMETRY

• Is the study of the relative quantities of reactants and products in a chemical reaction.

• The word (? ) was derived from two Greek words stoikheion which means “elements” and metron which means “to measure”.

Pressure

is defined as a force per unit area. The SI unit for pressure is pascal (Pa), named in honor of the French mathematician and philosopher, Blaise Pascal. (atm, torr, mm Hg)

Boyle’s Law

• P1V1 = P2V2

  • at constant T, as pressure increases volume decreases

Charles Law

• at constant p, as volume increase, temp increase

• v1/t1 = v2/t2

Gay- Lussac’s Law

• p1t1 = p2/t2

  • at constant v, as pressure increases, temp increases

GAS STOICHIOMETRY

Involve mass relationships in chemical reactions, where gas is either a reactant or a product.

Diffusion

The process by which gas molecules spread out and mix with other gases due to their random motion.

Effusion

The process by which gas particles pass through a tiny hole (without collisions with other particles) into a vacuum.