TEXES Science Chemistry 015 Chemical Equations & Reactions

reactants

starting chemicals in a chemical equation; left of arrow

products

ending chemicals in a chemical reaction; right of arrow

law of conservation of mass

matter is neither created nor destroyed; the form of matter may change but the total amount of matter stays constant; mass of reactant = mass of products

balanced equation

a chemical equation in which there are equal numbers of each type of atom on each side of the equation

coefficient

a number placed in front of a compound in an equation that indicates the number of atoms/molecules/formula units involved in a chemical reaction

synthesis

reactants combine to produce one compound; one product

decomposition

a reactant breaks down into two or more components; one reactant

single replacement

a single element takes the place of another element in a compound; an element and a compound produce a different element and compound

double replacement

elements in two compounds switch places; two compounds make two different compounds

Endothermic

a reaction that absorbs energy

Exothermic

a reaction in which energy is released

Activation energy

The minimum amount of energy needed to start a chemical reaction

Factors that control the rate of a reaction

temp, surface area, concentration, catalyst or inhibitors

Catalyst

Any substance that speeds up the rate of a reaction

Inhibitor

Any substance that slows down the rate of a reaction

Concentration

The amount of a substance in a given volume

Common ions

Sodium (Na+) Potassium (K+) Chlorid (Cl-) Calcium (Ca+) Iron (Fe+) Posphorous (P-)

Binary compound

composed of two elements first write the symbol of the cation and then the anion. Then add subscripts as needed to balance charges.

Mass ratio

Writing formulas

Naming compounds

Mole

representative particles of of a substance. SI unit for measuring the amount of a substance

Avogadro's number

Converting Number of Atoms to moles

Calculate number of moles to atoms

moles -> molecules -> atoms

Molar Mass

the mass of a mole of an element.

Mole to Mass

Determine the mass, in grams, of 9.45 moles of aluminum oxide (Al2O3).

Convert Mass to Moles

Calculate how many moles of iron(III) oxide are contained in 92.2 grams of pure Fe2O3.

Avogadro's Law

equal volumes of gases at a given temperature and pressure contain equal numbers of molecules.

Using Avogadro's Law

Determine the volume, in liters, of 0.60 moles SO2 gas at STP.

Molar Mass STP

The density of a gaseous compound containing carbon and oxygen is found to be 1.964 g/L at STP. What is the molar mass of the compound?

Percent Composition

the relative amounts of the elements in a compound. must add up to 100%.

Calculating Percent Composition

Percent Composition From a Formula

Calculate the percent composition of propane (C3H8).

Mass from Percent Composition

Calculate the mass of carbon and the mass of hydrogen in 82.0 grams of propane (C3H8).

Calculating Empirical Formula,

A compound is analyzed and found to contain 25.9% nitrogen and 74.1% oxygen. What is the empirical formula of the compound?

Molecular Formulas

shows the actual numbers of atoms in a molecule of the compound.

Calculating Molecular Formula

Calculate the molecular formula of a compound whose molar mass is 60.0 g/mol and empirical formula is CH4N.

Balancing a Chemical Equation

Determine the number of atoms of each element in the reactants and products. Count polyatomic ion as a single unit. If it is unchanged on both sides.
Begin by balancing elements that appear on both sides.
Do not change subscripts.

Polyatomic Ion

An ion made of two or more atoms

Combination Reaction

a chemical change in which two or more substances react to form a single new substance

Decomposition Reaction

a reaction in which a single compound breaks down to form two or more simpler substances

Single Replacement Reaction

a chemical change in which one element replaces a second element in a compound

Double Replacement Reaction

a chemical change that involves an exchange of positive ions between two compounds

Precipitate Reaction

Reaction that produces a precipitate

Combustion Reaction

occurs when a substance reacts with oxygen to produce energy in the form of heat and light

Chemical Reactivity

bleach

Sodium hypochlorite is the chemical name for

Ammonia

NH3

Baking soda

NaHCO3