Atoms and Foundation of Chemistry - Chapter 1 & 2 Review

Relative Atomic Mass

• Symbol is Aᵣ

• Average weighted mass of the atoms of an element compared with 1/12 of the mass of a carbon-12 atom.

Mole

• Avogadro’s Number (6.0×10²³ /mol)

• Number of specified entities as there are atoms in exactly 12.0g of Carbon-12.

Relative Formula Mass

The sum of the relative atomic masses of the atoms in the formula unit of an ionic compound. 

Molar Mass

• Mass of 1 mol of a substance.

• Equal to it’s relative molecular or formula mass in grams.

Limiting and Excess Reagent

• Limiting reagent: completely used up first in a reaction, thus determining the maximum amount of product formed. Determines maximum yield. 

• Excess reagent: remains after the limiting reagent is used up.

Types of Yields (3)

• Theoretical Yield: Calculated maximum amount of product that could form form a given amount of reactants.

• Actual Yield: Amount of product actually obtained from a reaction.

• Percent Yield: Percentage of Actual over Theoretical. 

Percent Composition by Mass

Percentage by mass of each element present in a compound.

Empirical Formula

Simplest whole-number ratio of atoms each element in a compound.

Molecular Formula

Actual number of atoms of each element present in a molecule.

Ions

A charged particle formed when an atom or compound loses or gains electrons. 

Anions are negative. Cations are positive. 

Spectator Ions

Ions that do not react or change state in a reaction. 

Solution

A homogenous mixture of a solute dissolved in a solvent.

Concentration

• Symbol is C

• The amount of solute per unit volume of a solution.

• Mol/dm³

Molarity

• A way of expressing concentration.

• Mol/dm³

Molar Gas Volume

• Symbol is Vm

• The volume occupied by 1 mol of gas at a certain pressure and temperature.

• At RTP: 24.0 dm³/mol

• At STP: 22.4 dm³/mol

RTP and STP

• Room Temperature and Pressure (25 Celsius, 298 Kelvin, 1.01×10^5 Pascals)

• Standard Temperature and Pressure (0 Celsius, 273 Kelvin, 1.01×10^5 Pascals)

• 1 atm for both.