Exam 2 Chem 101 BYU

ionic bond

Metal + nonmetal

covalent bond

Nonmetal + nonmetal

cation

positively-charged ions; formed when a metal loses electrons, and a nonmetal gains those electrons

anion

negatively-charged ions; formed when a metal loses electrons, and a nonmetal gains those electrons

polyatomic ion

ended in -ate, or -ite. has oxygen present

monoatomic ions

IA and IIA family

ionic compounds

ion bonding- positively and negatively charged ions together formed from strong electrostatic interactions between ions.

-high melting points

lewis structure

dot structure diagrams with valence electrons

valence electrons

determined by column they are in periodic table.

octet rule exceptions

H2: requires only 2 electrons

BCl3: the B only has 3 valence electrons to share.

B is stable with only 6 electrons

Br, P, S, Cl, and I can form molecules which they share more of their valence electrons- can expand to 10, 12 0r 14 electrons

double and triple bonds

when number of valence electrons is not enough to complete the octets of all of the atoms in the molecule.

one or more lone pairs is attached to central atom.

covalent compounds (molecules)

where bonds have electrons that are shared between atoms

how does VSEPR predict electron geometry and shape in Lewis structure?

to determine shape, you draw the Lewis structure; and then determine the number of bonding groups and lone pairs on the central atom to determine the shape

most electronegative atom

Florine (F)

polar

odd number of atoms- pulled in one direction

is a bent shape polar or non-polar?

polar

non-polar

even number of atoms- the ways it is being pulled cancel out evenly.

cation groups

1, 2, and 3

anion groups

5, 6, and 7

non-polar electronegativity

0-0.4

polar electronegetivity

0.5-1.8

ionic electronegetivity

1.8 < and higher

dipole bond

polar covalent bond that has a separation of charges. positive and negative ends of the dipole indicated by greek letter and then use an arrow to point FROM positive charge TO negative charge to indicate dipole

dipole-dipole attraction

POLAR molecules. occurs between the positive end of one molecule and the negative end of another. ex) HCl, H is partially positive and HCL molecule attracts partially positive negative Cl atom in another HCl molecule

hydrogen bonds***

POLAR molecules containing hydrogen atoms bonded to highly electronegative atoms of N, O, or F. ex) NH3

**strongest type of attractive forces b/w polar covalent molecules

dispersion forces

NONPOLAR compounds form solids at low temperatures. very weak attractions b/w nonpolar molecules. ex) Cl2 (melting point= -101); F2 (melting point= -220)

reactants

left side of the arrow

products

on the right side of the arrow

coefficients

numbers in front of a balanced formula. ex) 2H2 means there are 4 atoms of H

phases

solid, liquid, gas, aqueous

balance chemical equations

PRACTICE

combination

combining two or more elements/compounds to form one product.

ex) S + O --> SO2

decomposition

reactant splits into two or more simpler products.

ex) 2HgO --> 2Hg + O2

single replacement

reacting element switches place with an element in the other reacting compound

ex) A + BC --> AC + B

double replacement

positive ions in the reacting compounds switch places.

ex) AB + CD = AD + CB

combustion

carbon-containing compound, usually fuel, burns in oxygen from the air to produce CO2, H2O, and energy in the form of heat.

ex) CH4 + 2O2 --> CO2 + 2H2O+energy

oxidized reaction

OIL RIG

oxidized is loosing electrons

reduction reaction

OIL RIG

reduction is gaining electrons

avogadros number

6.02 x 10^23

how do you calculate molar mass of elements, molecules, and compounds?

look at molar mass on periodic table of each atom, add together all of their masses, considering if they have multiple atoms. LOOK AT PERIODIC TABLE

ex) 1 mole Carbon atom has a mass of 12.01 grams.

using molar mass to convert between grams and moles

given moles, need grams:

find molar mass of atom (in grams) and do conversion of moles to grams

mole-mole ratios

regards to coefficients in balanced equation of the reactants and products.

ex) 2Fe + 3S (ratio would be 2 moles Fe/3 moles S)

calculating limiting reactants

analyze what is given and needed in problem, do conversions (grams>molar mass>moles>mole-mole factor> moles> molar mass>grams) after calculations of doing with 2 DIFFERENT elements/grams, should get an answer. answer with lowest number is the limiting reactant.

percent yield

(actual yield/ theoretical yield) x 100%

theoretical yield which is the amount of the product

exothermic

negative

energy out!!!

energy of the products is lower than the reactants

endothermic

energy in!!!

positive

energy of the products is higher than the reactants (think about a graph)

calculating total energy of a reaction when given delta H and mass of reactants

look at page 278 in the book for an example

kinetic molecular theory of gases

model for the behavior of a gas

part 1

a gas consists of SMALL particles (atoms or molecules) that MOVE RANDOMLY with HIGH velocities

part 2

the ATTRACTIVE FORCES between the particles of a gas are usually very SMALL

part 3

the actual volume occupied by gas molecules is extremely small compared with the volume that the gas occupies

part 4

gas particles are in constant motion, moving RAPIDLY in STRAIGHT paths

part 5

the average kinetic energy of gas molecules is PROPORTIONAL to the Kelvin temperature

converting pressure, temperature, and volume to different units

atm. or mmhg; convert degrees Celcius or Farenheight to Kelvin; volume in L. (1L= 1000 mL) *divide by 1000 to get to L

atmospheric pressure

pressure exerted on us; in higher altitudes, the atmospheric pressure is less because there are fewer particles in the air.

Boyle's Law

P1V1=P2V2

Charle's Law

V1/T1= V2/T2

Gay-Lussac's Law

P1/T1=P2/T2

Combined Gas Law

P1V1/T1=P2V2/T2

Avogadro's Law

V1/N1=V2/N2

STP and molar volume

(273 K) is standard temp, standard pressure = 1 atm. Together abbreviated STP.

Ideal Gas Law

PV=nRT

n=moles

R=gas constant (given)

partial pressure

pressure a gas would have exerted if it were the only gas in the container.

Dalton's Law

Pt= P1 + P2 + P3... etc

total pressure of gas mixture= sum of the partial pressures of the gases in the mixture

** you can rearrange the equation if solving for a partial pressure**

ex) P(He)= Ptotal - P (O2)

convert the units to match and solve for unknowns. substitute pressures to calculate partial pressure.