Principles of Chemistry Exam 1 - University of Iowa

Scientific Law

A statement that describes what scientists expect to happen every time under a particular set of conditions

Scientific Theory

A well-tested explanation for a wide range of observations or experimental results.

Types of Matter

Solid, liquid, gas

Characteristics of Solid

Definite shape, definite volume, not compressible, high density

Characteristics of Liquid

Indefinite shape and definite volume

Characteristics of Gas

Indefinite shape and indefinite volume

Pure Substances

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties

Elements

A molecule composed of one kind of atom; cannot be broken into simpler units by chemical reactions.

Compound

A substance made up of atoms of two or more different elements joined by chemical bonds

Homogeneous mixture

A mixture that is uniform in composition; components are evenly distributed and not easily distinguished

Homogeneous Mixture Example

Salt water

Heterogeneous Mixture

A mixture that is not uniform in composition; components are not evenly distributed throughout the mixture

Heterogeneous Mixture Example

Oil and water

Atoms

Building blocks of matter

Molecules

Groups of two or more atoms held together by chemical bonds

Sig Figs

All the digits that can be known precisely in a measurement, plus a last estimated digit

Uncertainty in Measurement

A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty.

Accuracy in Measurement

A description of how close a measurement is to the true value of the quantity measured.

Precision of Measurement

The exactness of a measurement

Metric units of length

Kilometer (km)

Meter (m)

Decimeter (dm)

Centimeter (cm)

Millimeter (mm)

Micrometer (um)

Nanometer (nm)

Metric units of volume

Liter (L)

Milliliter (mL)

Metric units of mass

Grams and kilograms

Metric units of temperature

Kelvin (K)

Conservation of Mass

The principle stating that matter is not created or destroyed during a chemical reaction

Law of Composition

A given compound always has the same composition, regardless of where it comes from

Law of Multiple Proportions

If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

Dalton's Atomic Theory

1) elements are composed of atoms. 2) atoms of same element are identical, but differ from other elements. 3) elements can mix together 4) atoms only change when mixed with other elements

Atomic Number

Number of protons

Mass Number

The sum of the number of neutrons and protons in an atomic nucleus

The number on the bottom

How to calculate Protons

The number in the top

How to calculate neutrons

Mass number - atomic number

How to calculate electrons

Atomic number

Structure of atoms

Protons, neutrons, electrons

Symbol

The letter or letters that represent an element

Isotopes

Atoms with the same number of protons, but different numbers of neutrons

Examples of Isotopes

Carbon-12, Carbon-13, Carbon-14

Average atomic mass formula

(Percent to decimal)(mass) + (percent to decimal)(mass)

Isotopic abundance formula

(mass)(x) + (mass)(1-y), then solve for x and y by substituting

Periodic Table Trends: Moving L to R

Atomic radius decreases, ionization energy increases, electronegativity increases.

Period Table Trends: Moving Top to Bottom

Atomic radius increases, ionization energy decreases, electronegativity increases

Information given from Chemical Formula

Symbols of the reactants and products, show the physical state of a substance, and if the formula is balanced

Empricial formula

A formula giving the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms.

Molecular Formula

A chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms.

Molecular formula (picture) : Ch4

Structural formula (picture): Ch4

Ball and Stick Model: Ch4

Space-filling model: Ch4

Ions

Positively and negatively charged atoms

How are ions formed?

When atoms lose or gain electrons

How do you determine the charges of ions?

By the groups

Ionic compound

A compound that consists of positive and negative ions

Examples of Ionic compounds

NaCl, MgO

Covalent compound

An element or chemical compound in which atoms are held together by covalent bonds

Examples of Covalent compounds

SO4, ClO3

Binary Acid

An acid composed of only two elements, one of which is hydrogen

Oxyacids

Acids that contain hydrogen, oxygen, and a third element usually a nonmetal.

How to write Binary acid

hydro + element+ ic acid

How to write Ionic Compounds (1 oxidation state)

Metal + Nonmetal + ide

How to write Ionic Compounds (2+ Ions)

Metal name(oxidation state as Roman numeral in parenthesis) + nonmetal name + ide

How to write Molecular Compounds (nonmetal + nonmetal)

(Prefix + 1st element) + (prefix + 2nd element name with ide)

Polyatomic Ions

Ions that are made of more than one atom

How to write Binary Aqueous Acids

hydro + element name with ic + acid

How to write Oxoacids

element name + suffix + acid

-ate to

-ic

-ite to

-ous

1+ Charged Cations

H+ Hydrogen Ion

Li+ Lithium Ion

Na+ Sodium Ion

K+ Potassium Ion

Ca+ Calcium

Ag+ Silver Ion

NH4+ Ammonia Ion

Cu+ Copper(I)

2+ Charged Cations

Mg++ Magnesium Ion

Ca++ Calcium Ion

Sr++ Strontium Ion

Ba++ Barium Ion

Zn++ Zinc Ion

Cd++ Cadmium Ion

Co++ Cobalt(II)

Cu++ Copper(II)

Fe++ Iron(II)

Mn++ Manganese(II)

Hg++ Mercury(II)

Ni++ Nickel(II)

Pb++ Lead(II)

Sn++ Tin(II)

3+ Charged Cations

Al+++ aluminum Ion

Cr+++ Chromium(III)

Fe+++ Iron(III)

1- Charged Anions

H- hydride Ion

F- Fluoride Ion

Cl- Chloride Ion

Br- Bromide Ion

I- Iodide Ion

CN- Cyanide Ion

OH- Hydroxide Ion

C2H3O2- Acetate Ion

ClO3- Chlorate Ion

ClO4- Perchlorate Ion

NO3- Nitrate Ion

MnO4- Permanganate Ion

3- Charged Anion

N--- Nitride Ion

PO4--- Phosphate Ion

2- Charged Anion

O-- Oxide Ion

O2-- Peroxide Ion

S-- Sulfide Ion

CO3-- Carbonate Ion

CrO4-- Chromate Ion

Cr2O7-- Dichromate Ion

SO4-- Sulfate Ion

How are balanced chemical equations symbolic representations?

They are symbolic representations of chemical and physical changes

Reactants

Products

Decompostion Reactions

Combination Reactions

Two or more substances react to form one product

Combustion Reaction Examples

Combustion Reaction

A chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light

Calculate molecular weight

Use dimensional analysis (g/mol)

Formula/Molecular weight

Sum of the atomic mass of the atoms in the chemical formula of a substance

Percent Compostion

The percent by mass of each element in a compound

Percent Composition formula

% composition = (# of atoms of an element)(atomic weight of element) / (formula weight of substance)

Molar Mass

The mass of one mole of a substance in grams

Avogadro's number

number of representative particles in a mole

6.022 * 10^23

Molar Mass Example

K2O

2 mols K x 39g=78g

1 mol O x 16g=16g

ADD THOSE TOGETHER

MM=94g/mol

Interconverting Grams to Moles

Use Molar Mass

Interconverting Moles to Formula Units

Use Avogadro's Number

Empricial Formula

A formula giving the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms.

Use Empricial Formula to find Molecular Formula

1. Calculate the empirical formula mass.

2. Divide the gram molecular mass by the empirical formula mass.

3. Multiply each of the subscripts within the empirical formula by the number calculated in Step 2.

Use Molecular Formula to find Empricial Formula

1. Get the mass of each element by assuming a certain overall mass for the sample (100 g is a good mass to assume when working with percentages

2. Convert the mass of each element to moles

3. Find the ratio of the moles of each element

4. Find the ratio of the moles of each element.

5. Use the mole ratio to write the empirical formula, Multiplying the mole ratios by two to get whole number

Mole Ratio

A conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction

Mass to Mass Conversions

Mass A --> Moles A --> Moles B --> Mass B

Limiting Reactant

The substance that controls the quantity of product that can form in a chemical reaction

Why can 1 limiting reactant limit the yield of the product?

Because once it's all used up the reaction can't continue to form the product.

Calculate excess reactant

1. Write the chemical equation

2. Calculate the moles of product from the first reactant.

3. Calculate the moles of product from the second reactant.

4. Identify the limiting reactant and the excess reactant.

5. Calculate the mass of excess reactant used up.

6. Calculate the mass of unused excess reactant.

7. Calculate the mass of limiting reactant needed to react with the unused excess reactant.

Theorectical yield

The maximum amount of product that can be produced from a given amount of reactant

Actual Yield

The measured amount of a product obtained from a reaction

Percent Yield

The ratio of the actual yield to the theoretical yield expressed as a percent

actual yield/theoretical yield x 100

Electrolytes

Substances that release ions in water

Nonelectrolytes

Substances that form no ions in water and cannot conduct electricity