Unit 3: Chemistry Calculations - The Mole Concept

These flashcards cover essential vocabulary and concepts related to the mole concept and stoichiometry in chemistry.

The Mole Concept

Establishes the relationship between mass of a substance and number of particles it contains.

Mole

A unit representing a specific number of particles (approximately $6.02 imes 10^{23}$).

Avogadro's Number

The number of particles in one mole, approximately $6.02 imes 10^{23}$.

Molar Mass

The mass of one mole of a substance, expressed in grams per mole (g/mol).

Unit for Molar Mass

Expressed in grams per mole (g/mol).

Atomic Mass of Sodium (Na)

22.99 g/mol.

Atomic Mass of Gold (Au)

196.97 g/mol.

Molar Mass of H2O

18.02 g/mol.

Formula for Molar Mass of a Compound

Sum of the atomic masses of all elements in one molecule.

Calculation of Moles of Elements

Determining the amount of each element within a compound.

Moles of Hydrogen in H2O

2 moles of Hydrogen (H) in 1 mole of H2O.

Mass of Hydrogen in H2O

2.02 g in one mole of H2O.

Mass of Oxygen in H2O

16.00 g in one mole of H2O.

Composition of CaCO3

1 mole of Calcium (Ca), 1 mole of Carbon (C), 3 moles of Oxygen (O).

Total Molar Mass of CaCO3

100.09 g/mol.

Calculating Moles from Mass

Number of Moles = Mass / Molar Mass.

Find moles in 24.02 g of Carbon (C)

2 moles.

Mass from Moles Formula

Mass = Number of Moles × Molar Mass.

Moles of H2O in 10 g

Approximately 0.55 moles.

Volume of Gas at STP

1 mole occupies 22.4 Liters.

Standard Temperature and Pressure (STP)

0 °C = 273.15 K and 1 atm, where 1 mole of gas occupies 22.4 L.

Percentage Composition Definition

Indicates the proportion of each element's mass within a compound.

Calculation Principle for Percentage

Divide the part by the whole and multiply by 100.

Percent mass of an element

(Grams of element / Grams of compound) * 100.

Molar Mass of CaCO3 Calculation

100.09 g/mol.

Percent Calcium in CaCO3

Approximately 40.04%.

Empirical Formula Definition

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

Molecular Formula Definition

Actual number of atoms of each element in one molecule of a compound.

Relationship Between Empirical and Molecular Formulas

Molecular formula is a whole-number multiple of the empirical formula.

Chemical Change Definition

A process in which a new substance is formed.

Chemical Reaction Definition

The process that occurs during a chemical change.

Reactants

Substances that start the reaction, typically on the left side.

Products

Substances formed as a result of the reaction, typically on the right side.

Balanced Equation Purpose

To adhere to the Law of Conservation of Mass.

Combination Reaction Definition

Two or more reactants combine to form a single new substance.

Decomposition Reaction Definition

One substance breaks down to form two or more new substances.

Single Replacement Reaction Definition

One element replaces another element in a compound.

Double Replacement Reaction Definition

An exchange of positive ions between two compounds.

Neutralization Reaction Definition

An acid and a base react to form water and a salt.

Combustion Reaction Definition

An element or compound reacts rapidly with oxygen, producing energy.

Exothermic Reaction Definition

Reactions that release energy into the surroundings.

Endothermic Reaction Definition

Reactions that absorb energy from the surroundings.

Activation Energy Definition

The minimum amount of energy required to start a chemical reaction.

Stoichiometry

The branch of chemistry concerned with measuring amounts of reactants and products.

Limiting Reactant Definition

The reactant present in insufficient amount that determines the amount of product formed.

Calculation Example: Haber-Bosch Process

N2 + 3H2 → 2NH3.

Find moles of NH3 produced from N2

6 moles NH3.

Identify Limiting Reactant

The reactant that produces the least amount of product.

Conclusion from H2 limiting reactant example

H2 is the limiting reactant, producing 4 moles of NH3.

Molecular Formula of Adipic Acid

C6H10O4.

Chemical Equations

Shorthand representation of a chemical reaction.

Balancing Chemical Equations Method

Trial and error (hidden trial method).

Skeleton Equation Definition

An unbalanced chemical equation.

Molar Mass of Cl2

70.90 g/mol.

Mass of Cl2 in 4.50 L at STP

Approximately 14.25 g.

Density Formula

Density = Mass / Volume.