Unit 1 - Chem Basics

Question 1

Dalton’s Atomic Theory

Answer 1

• atoms are the smallest particles: false, there are subatomic particles
• atoms are indivisible: false, there are protons, neutrons, electrons
• atoms of a given element are identical so they have the same mass and properties: false, isotopes exist so not identical and not same mass, atoms can change their identity during nuclear reactions where 238U -> 234Th + 4He
• atoms combine in whole number ratios: false
  some have non-integer ratios

Question 2

Fundamental Unit of Charge

Answer 2

1.602 x 10^-19 Coulomb (C)

So if a question asks you what is the charge of a specific ion, it would be positive or negative ___ multiplied by that number

Ex:
What is the charge of a Li+ ion?
a) +1 C
b) +1.602 × 10−19 C
c) +3 C
d) +4.806 × 10−19 C

it is b because 1 x 1.602 x 10^-19 is 1.602 x 10^-19 and positive charge

Question 3

Mass of Subatomic Particles

Answer 3

proton: 1.00728 amu
neutron: 1.00867 amu
electron: 5.486 * 10^-4

Question 4

Amu to Kg

Answer 4

1 amu = 1.660540*10^-27 kg

Question 5

How do you find the mass of a certain atom?

Answer 5

1. Look at their atomic mass
2. atomic mass = n + p
3. # p = #e-
4. do #p * 1.00728 + #n + #e- * 5.486 * 10^-4

this is the predicted mass!

Question 6

Atomic Symbols

Answer 6

A/Z X
X = one or two letter symbol for the element
A = mass number = #p + #n
Z = atomic number = #p

Question 7

Missing mass

Answer 7

missing mass = predicted mass - measured mass

The missing mass (mass deficit) was converted to nuclear binding energy (holding neutrons and protons together) by the equation E = mc^2

the missing mass <= 1% for all cases, but it is difficult to predict precisely. Thus, the best value for atomic mass are measured experimentally

Question 8

Isotopes

Answer 8

• have the same #p (b/c same element) but diff #n
• results in diff mass

Question 9

Natural Abundance

Answer 9

• the relative amount of various isotopes present on earth
• must add to 100%

Question 10

Average Atomic Mass

Answer 10

M = a1m1 + a2m2 + …

where
a1 + a2 + … = 1

remember to convert percents to decimal form

the atomic mass listed on the periodic table is the avg atomic mass of all naturally occurring isotopes of a given element

Question 11

Electronegativity (χ, chi)

Answer 11

the ability of an atom in a compound to attract electrons to itself
- higher to the right and up on the periodic table excluding the last column (noble gasses) because they already have 8 electrons, so fluorine has highest electronegativity

Question 12

Non-polar Covalent Bond

Answer 12

• nonmetal and nonmetal
• sharing of electrons is equal
• can also be homonuclear nonpolar covalent bond which is a bond between two of the same atoms

Question 13

Polar Covalent Bond

Answer 13

nonmetal and nonmetal
- Unequal sharing of electrons due to difference in electronegativity
- Results in partial charges
- |χA - χB| <= 2

Question 14

Ionic Bond

Answer 14

• Δχ >= 3
• nonmetal + metal
• e- is taken completely away from one atom by the other
• bonds form ionic compounds
• 2 < Δχ < 3 is a grey area so must refer to an experiment to determine the bond

Question 15

Compount Type: Molecular

Answer 15

• contains only covalent bonds
• form molecules

Question 16

Compound Type: Non-molecular

Answer 16

• ionic bonds exist only in non molecular lattices
• form ionic compounds

Question 17

Oxidation Numbers

Answer 17

• one way to assess the charge of an atom when it forms and ion or a covalent bond
• expressed as numbers like [-1] or in roman numerals like [+VI]

Question 18

Ox # Rules

Answer 18

1. pure element in its natural state: 0, free and uncombined
   Ex: O2, Fe
2. Single ion with charge (monoatomic ion): Ox # = same as charge
   Ex: Na+ is +1 and S^2- is -2
3. Fluorine is always -1
4. Columns 1 and 2: it is the column number and positive
   Ex: Li is +1 and Mg is +2
5. Hydrogen is always +1 with the exception of metal hydrides where it is -1
6. Oxygen is almost always -2 with the exception of O-O and O-F bonds like in H2O2 it is -1
7. In groups 13-18 (columns 13-18), the oxidation # is USUALLY 8-second # in group #. (like 8-3). This is not true for ones lower down in the column so this is technically not a rule but you do have to know the ox # for ones in those columns higher up so this works. sign will just be whatever u need
   Ex:
   in CH4 carbon is +4, in BH3 boron is +3

The ox # in a neutral compound must sum to 0

Question 19

Halogen

Answer 19

Group 17 elements that are highly reactive, nonmetallic, and form salt when they react with metals

Question 20

Empirical Formula

Answer 20

Smallest repeating unit in a compound

Question 21

Molecular Formula

Answer 21

Exact # of atoms of each element in one molecule

Question 22

Mole

Answer 22

• name for 6.022*10^23
• symbol is No or Na
• 1 mole of ethanol is 6.022*10^23 ethanol molecules

Question 23

Molar Mass

Answer 23

Do the avg molecular mass (g/mol) found on the periodic table of each atom times the number of each atom

Ex:
C2H6O

C(12.011 g/mol) +
6(1.0079 g/mol)+
1(15.999 g/mol)
= 46.098 g/mol

Question 24

number of moles

Answer 24

mass/molar mass

Ex:
100g/46.068 g/mol = 2.1707 mol

Question 25

density

Answer 25

d = m/V Ex: the density of ethanol is 0.789 g/mol, what is the volume of 100g ethanol? V = 100g/0.789g/ml = 127 ml A cube of BaF2 contains 1.10x10^24 F- ions and measures 3.2cm on one edge. What is the density in g/cm^3? 1.10*10^24 F- ions * (1 mol F2)/(6.022 x 10^-23) * (1 mol BaF2/2 mol F2) * (175.32 g/mol)/(1 mol BaF2) = 160.1g d = m/V = 160.1g/3.2^3cm = 4.888g/cm^3 *get molar mass from periodic table* *remember that you have to do mole ratios to cancel stuff out aka theres 2 moles F2 in 1 mole BaF2* *remember that density is temperature dependent aka less dense at hotter temps*