Chapter 4: Compounds & Stoichiometry (7%)

molecular weight

Molecular Weight vs. Formula Weight vs. Molar Mass

The sum of all the atomic weights of all the atoms in a molecule

Measured in amu/molecule

formula weight

Molecular Weight vs. Formula Weight vs. Molar Mass

The sum of all the atomic weights of all the ions in an ionic compound according to its empirical formula

Measured in amu/molecule

Numerically the same as molar mass but used in different applications

molar mass

Molecular Weight vs. Formula Weight vs. Molar Mass

The mass of one mole of a compound

Usually measured in g/mol

Numerically the same as formula weight but used in different applications

Avogadro’s Number

Represents the exact number of particles (atoms, molecules, ions, or electrons) contained in one mole of any substance

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

molarity, M, molarity, M, mole

Normality (N) is related to __________ (___) by multiplying the __________ (___) by the number of equivalents per _____ of compound

N = n x M

(n = the # of dissociable protons H⁺ / molecule of acid)

Molarity & Normality

Write out the relationship between Normality (N) and Molarity (M)

hydrogen, 1, H+, 1, H+

Normality

A 1 N solution of acid contains a concentration of ____________ ions = to ___ mole(s) of ____ per liter of solution

This is because a 1 N solution contains exactly ___ equivalent(s) of ____ per liter of solution

hydrogen, 2, H+, 2, H+

Normality

A 2 N solution of acid contains a concentration of ____________ ions = to ___ mole(s) of ____ per liter of solution

This is because a 2 N solution contains exactly ___ equivalent(s) of ____ per liter of solution

1 M, 1

(HCl is monoprotic, so 1x equivalent of base are required to neutralize the single proton of the acid)

Molarity & Normality

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

(H₂CO₃ is diprotic, so 2x equivalents of base are required to neutralize both protons of the acid)

Molarity & Normality

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

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

equivalents

The amount of a substance (in moles) that reacts with, combines with, or is equal to one mole of another substance

Often defined by the number of electrons or hydrogen ions it donates or accepts in a reaction, essentially representing its reactive capacity.

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

Law stating that any sample of a PURE chemical compound ALWAYS contains the SAME ELEMENTS in the SAME FIXED RATIO by MASS, regardless of its source or preparation method

empirical formula

Empirical Formula vs. Molecular Formula

The smallest whole-number ratio of the elements in a compound

EX: 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

EX: C6H6

C3H4O3, C9H12O9

Empirical & Molecular Formulas

What are the EMPIRICAL & MOLECULAR formulas of a carbohydrate that contains 40.9% carbon, 4.58% hydrogen, and 54.52% oxygen & 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) x 100

Percent Composition

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

33%

Percent Composition

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

combination

Types of Reactions

WORD BANK: Combination, Decomposition, Neutralization, Combustion, Single-Displacement, Double-Displacement

——

When two or more reactants combine to form one product

A+B→C

decomposition

Types of Reactions

WORD BANK: Combination, Decomposition, Neutralization, Combustion, Single-Displacement, Double-Displacement

——

When one reactant is chemically broken down into two or more products

A→B+C

combustion

Types of Reactions

WORD BANK: Combination, Decomposition, Neutralization, Combustion, Single-Displacement, Double-Displacement

——

When a fuel and an oxidant (typically oxygen) react, forming the products water and carbon dioxide (if the fuel is a hydrocarbon)

Fuel + O₂ → CO₂ + H₂O + Energy (heat/light)

single-displacement

Types of Reactions

WORD BANK: Combination, Decomposition, Neutralization, Combustion, Single-Displacement, Double-Displacement

——

When an ion of one compound is replaced by an atom/ion of another element

Often further classified as oxidation-reduction reactions

A + BC → AC + B

double-displacement

Types of Reactions

WORD BANK: Combination, Decomposition, Neutralization, Combustion, Single-Displacement, Double-Displacement

——

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

Usually happen in water

Often result in a visible change, such as the formation of a solid precipitate, a gas, or water

AB + CD → AD + CB

neutralization

Types of Reactions

WORD BANK: Combination, Decomposition, Neutralization, Combustion, Single-Displacement, Double-Displacement

——

When an acid reacts with a base to form a salt (and usually water)

H⁺ + OH^- → H₂O + salt

Law of Conservation of Mass

Law stating that the # of atoms of each element on the reactant side MUST EQUAL the # 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

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

limiting reagent

The reactant that will be consumed first (gets completely consumed) in a chemical reaction

Determines & limits the maximum amount of product that can be formed

excess reagents

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

theoretical yield

the max amount of product that can be formed in a chemical reaction, 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 (m) / molar mass (MM)

Write out the formula for calculating the # of moles of an element in a sample

Variables: mass of a sample (m), molar mass (MM)

GEW = molar mass of compound (MM) / number of particles of interest produced or consumed per molecule of compound (n)

Write out the formula for calculating the Gram Equivalent Weight of a compound

Variables: molar mass of compound (MM), number of particles of interest produced or consumed per molecule of compound (n)

mass of compound (m) / gram equivalent weight

Write out the formula for calculating the # of equivalents present in a compound

Variables: mass of compound (m), gram equivalent weight

Molarity (M) = Normality (N) / n

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

Write out the formula for calculating molarity (M) from normality (N)

Variables: normality (N), of protons, hydroxide ions, electrons, or ions produced or consumed by the solute (n)

molecules

Ionic compounds do not form true ___________ because of the way in which the oppositely charged ions arrange themselves in the solid state as crystal lattices

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:

O^2-

nitride

Name the following ionic compound:

N^3-

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

A substance that produces ions when dissolved in a polar solvent (like water), allowing the solution to conduct electricity through the movement of these ions (cations and anions)

strong

Strong vs. Weak

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

weak

Strong vs. 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