Chapter 4: Compounds & Stoichiometry (7%)

molecular weight

the sum of all the atomic weights of all the atoms in a molecule measured in amu/molecule

formula weight

the sum of all the atomic weights of all the ions in an ionic compound according to its empirical formula measured in amu/molecule

molar mass

the mass of one mole of a compound; usually measured in g/mol

one mole

Avogadro’s number of particles = ____ ____ of a compound

6.022 × 10^-23 (particles)

Avogadro’s number

molecular/formula weight

One mole of a compound has a mass in grams equal to the ____________/__________ _________ of the compound in amu

equivalents

What does this question describe:

“How many moles of the thing we are interested in will one mole of a given compound produce”

3

How many equivalents of hydrogen does H3PO4 have?

1

How many equivalents of hydrogen does HCl have?

gram equivalent weight

the amount of a compound that produces one equivalent of the particle of interest measured in grams

normality

the ratio of equivalents per liter

molarity, molarity, mole

normality is related to __________ by multiplying the __________ by the number of equivalents per _____ of compound

hydrogen, 1

a 1 N solution of acid contains a concentration of ____________ ions equal to ___ mole per liter

hydrogen, 2

a 2 N solution of acid contains a concentration of ____________ ions equal to ___ mole per liter

1 M, 1

What is the molarity of HCl in a 1 N HCl solution?

How many equivalents of base are needed to neutralize this acid?

0.5 M, 2

What is the molarity of H2CO3 in a 1N H2CO3 solution?

How many equivalents of base are needed to neutralize this acid?

equivalents

moles of the species of interest

acid-base, oxidation-reduction

the 2 types of reactions where equivalents are most often seen

law of constant composition

states that any pure sample of a compound will contain the same elements in the same mass ratio

empirical formula

Empirical Formula vs. Molecular Formula

the smallest whole-number ratio of the elements in a compound; example CH; ionic compounds only have this formula type

molecular formula

Empirical Formula vs. Molecular Formula

either the same as or a multiple of the other formula; gives the exact number of atoms of each element in a compound; example C6H6

C3H4O3, C9H12O9

What are the empirical and molecular formulas of a carbohydrate that contains 40.9% carbon, 4.58% hydrogen, and 54.52% oxygen and has a molar mass of 264 g/mol? (pg. 131)

percent composition

the percent of a specific compound that is made up of a given element

mass of individual element / molar mass of compound

write out the formula for calculating the percent composition by mass of an element in a compound

33%

What is the approximate percent composition of chromium in K2Cr2O7? (pg. 130)

combination

type of reactions that occur when two or more reactants combine to form one product; A+B→C

decomposition

type of reactions that occur when one reactant is chemically broken down into two or more products; A→B+C

combustion

type of reactions that occur when a fuel and an oxidant (typically oxygen) react, forming the products water and carbon dioxide (if the fuel is a hydrocarbon)

displacement

type of reactions that occur when one or more atoms or ions of one compound are replaced with one or more atoms or ions of another compound

single-displacement

type of reactions that occur when an ion of one compound is replaced by an atom or ion of another element; often further classified as oxidation-reduction reactions

double-displacement

type of reactions that occur when elements from two different compounds trade places with each other to form two new compounds; occurs when one of the products is removed from the solution as a precipitate or gas or when two of the original species combine to form a weak electrolyte that remains undissolved in solution

neutralization

type of reactions that occur when an acid reacts with a base to form a salt (and usually water)

law of conservation of mass

states that the number of atoms of each element on the reactant side must equal the number of atoms of that element on the product side

balancing the least common atoms, balancing the more common atoms, balancing charge (if necessary)

list in order the 3 steps in balancing chemical equations

convert from the given units to moles, use the mole ratio, convert from moles to the desired units

list in order the 3 steps used in stoichiometry/dimensional analysis problems

its molar mass in grams (from the periodic table)

1 mole of any substance = ?

22.4 L

1 mole of any ideal gas at standard temp & pressure (STP) = ?

limiting reagent

the reactant that will be consumed first in a chemical reaction

excess reagents

the other reactants present in a chemical reaction aside from the limiting reagent

theoretical yield

the max amount of product generated that can be generated as predicted from the balanced equation, assuming that all of the limiting reactant is consumed with no side reactions

actual yield

the amount of product one actually obtains during a reaction

actual yield

Which is typically lower: theoretical yield or actual yield?

(actual yield / theoretical yield) x 100

write out the formula for calculating the percent yield

mass of a sample / molar mass

write out the formula for calculating the number of moles of an element using mass

molar mass of compound / number of particles of interest produced or consumed per molecule of compound

write out the formula for calculating the gram equivalent weight

mass of compound / gram equivaltent weight

write out the formula for calculating the number of equivalents present in a compound using mass

normality / n (# of protons, hydroxide ions, electrons, or ions produced or consumed by the solute)

write out the formula for calculating molarity from normality

molecules

ionic compounds do not form true ___________ because of the way in which the oppositely charged ions arrange themselves in the solid state

iron(II), ferrous

Name the following ionic compound:

Fe2+ (2 names)

iron(III), ferric

Name the following ionic compound:

Fe3+ (2 names)

hydride

Name the following ionic compound:

H-

oxide

Name the following ionic compound:

O2-

nitride

Name the following ionic compound:

N3-

nitrite

Name the following ionic compound:

NO2-

nitrate

Name the following ionic compound:

NO3-

poor, lattice, crystalline, lattice, ion-dipole, solution, conduct

Solid ionic compounds tend to be ______ conductors of electricity because the charged particles are rigidly set in place by the ________ arrangement of the ____________ solid. In aqueous solutions, however, the ________ arrangement is disrupted by the ____-_______ interactions between the ionic compounds and the water molecules. The cations and anions are now free to move, and as a result, a _________ of ions is able to ________ electricity.

electrolytes

Solutes that enable solutions to carry currents

strong

a solute is considered a _______ electrolyte if it dissociates completely into its constituent ions

weak

a solute is considered a _______ electrolyte if it ionizes or hydrolyzes incompletely in aqueous solution, and only some of the solute is dissolved into its ionic constituents

nonelectrolytes

compounds that do not ionize at all in water, retaining their molecular structure in solution; includes many nonpolar gases and organic compounds