AP CHEM Ch 1-3 Flashcards
Sig figs
Last figure is a guess. When adding and subtracting, use fewer number after decimal. When mult or dividing, use fewer number of sig figs in answer.
Prefixes:
Giga (10^9), Mega (10^6), Kilo (10^3), Deci (10^-1), Centi (10^-2), Milli (10^-3), Micro (10^-6), Nano (10^-9), Pico (10^-12)
Precision vs Accuracy
Precision is the degree of agreement between multiple measurements whereas accuracy is if the measurement is correct.
Precision indicates reproducibility–> whether or not you get the same result as last time
Accuracy indicates getting the center of the target, the correct value
Thin layer chromatography
A silica plate is placed in a solvent with spots of the sample on the lower end of the paper.
The mobile phase runs up the stationary phase (the paper), causing the sample to be dragged along with it.
This results in separation of materials as they interact w the stationary phase differently.
The dot that goes higher up is more like the solvent as the solvent runs to the top of the paper.
Retention factor
In TLC, the RF is the ratio of how far substance A goes / how far the solution travels up the paper. A RF closer to one indicates a substance more like the solvent.
Column chromatography
Good for organic compounds. Inside a column and the mobile phase is separated out from the stationary phase by gravity or air pressure.
Gravity filtration
Used with a funnel and a solution involving a precipitate. Pour the solution into the funnel paper and have a beaker collect the liquid while the solid is collected by the funnel.
Vacuum filtration
Used to isolate the precipitate. Uses a fritted funnel and a vacuum apparatus to pull solvent away from the precipitate.
Distillation
Boil the solution– lower boiling point boils first, travels through the condenser into the receiving flash
Good for homogeneous solutions w different boiling points among the components.
Density
Mass/ volume
Use balance and graduated cylinder (subtract differences in the volume)
Temperature unit conversions
T(K) = T(C) + 273 T(F) = 9/5 T(C) +32
Matter
Can it be physically separated? Yes- mixture Is the composition uniform? Yes - homogenous mixture (solution) No- heterogeneous (colloids or suspensions)
No-pure substance
Can it be chemically decomposed?
Yes- compound
No- element
Beginning of chem
Greeks were first to contemplate matter.
Democritus fostered second theory and Greeks said atoms were the ultimate particles
Boyle
First quantitative experiments– pressure and volume
Lavoisier
French scientist who discerned the Law of Conservation of Mass and wrote first chem textbook.
Law of conservation of mass
Mass is neither created nor destroyed in a chemical reaction
Joseph Proust
A given compound always contains exact same proportion of elements by mass. Law of Definite Proportions
Law Definite Proportions
Atoms combine in same ratio to form the same compound. Four atoms of lead combine w four atoms of sulfur to get four units of lead sulfide.
But if we had six atoms of sulfur, two atoms would be left.
Law of Multiple Proportions
If the two compounds are composed of the same two elements, the masses of the second element that combine with one gram of the first element will always be in a ratio reducible to small whole numbers.
You can have CO or CO2, where the ratio of O in CO2 to CO is 2:1
Dalton Atomic Theory
- Each element is composed of atoms
- Atoms of given element are identical (false, isotopes)
- Compounds are formed when different elements combine. A given compound always has the ratio of elements.
- A chemical reaction changes the arrangement or bonding of the atoms-doesn’t change the atoms (not true-redox)
Sterling silver has silver and copper and silver.
If mass is 105 g and volume is 10.12 mL, calc mass percent of copper.
Density of copper is 8.96 g/mL
Density of silver is 10.5 g/mL
X+Y=1
8.96x + 10.5 y = density (105/10.12)
Gay Lussac
At the same temperature and pressure, equal volumes of different gasses combine to form products.
Avagadro’s Hypothesis
Equal volumes of gas at the same P and T have same numbers of particles
JJ Thompson
Studied cathode ray tubes and when a high voltage was applied, a ray was produced. Ray was produced at negative electrode, measured a charge to mass ratio.
e/m = -1.76 * 10^8 C/g
Cathode ray tube
Cathode rays deflected by applied electric field away from negative plate.
Different metals produce a beam that behaves rhe same way.
Proved negative charge.
Thomson
Plum pudding model–
Positive pudding with negative electron plums throughout.
He postulated atoms had electrons and thus needed to have positive component in order to be neutral overall
Millikan
Oil drop experiments to get magnitude of electron charge.
Got the mass of an electron– 9.11*10^-31 kg
Rutherford
Used alpha particles to test plum pudding model
He found that rather than all of the positive charges going straight through, most of them did, but some were deflected at sharp angles and others at smaller angles off the nucleus. But most went through.
This showed there is a positive charged nucleus in the center
The atom
Protons, neutrons, electrons
Positive center- dense, the nucleus.
Atomic number–#protons
Neutral – equal number protons and electrons
Mass number
Symbolized by A
Protons plus neutrons
Isotopes
Different number of neutrons in atoms w the same protons
Carbon-14 is 6 protons and 8 neutrons whereas
Carbon-12 is 6 p and 6 n
Chlorine has 2 natural isotopes, chlorine 37 and chlorine 35
The reported mass is 35.45 amu. Get the percent natural abundance of the two isotopes
35x+37y=35.45
X+y=1
Chemical bonds
Forces holding atoms together as compounds
Covalent bonds
Between two non-metals
Share electrons
Molecules formed
Ionic bond
Transfer of an electron, force of attraction between oppositely charged species.
Anion
Negative ion
Cation
Positive ion
Metals
Left side of the periodic table Malleable Ductile Lustrous Lose electrons and become cations
Nonmetals
Right side p table
Gain electrons and become anions
Bond to each other to form covalent bonds
Alkali metals
Column 1
Very reactive
1+ cations
Alkaline earth metals
2nd group
Form +2 cations
Halogens
Diatomic molecules but also react w metals to gain electrons to become 1- anions
17 group
Noble gases
Group 18
Don’t bond, Unreactive
Columns
Groups or families
Similar chemical properties
Same number of valence electrons
Rows
Periods
Determines amount of electron shells
Naming binary compounds
Cation is first
Anion adds the “-ide” at the end
For transition metals, write the charge in parenthesis
Iron (II) Sulfide
Naming two non metals
Use prefixes
Carbon dioxide
Naming acids
If the anion ends in “-ide” then it is hydro—ic acid
HCl–> Hydrochloric acid
If the anion ends with “ate,” then we change it to “-ic”
H2SO4 –> Sulfuric acid
If the anion ends with “ite,” then change it to “-ous”
H2SO3 –> Sulfurous Acid
Mass spectrometry
Method that is used to compare masses of atoms
Atoms, molecules, or compounds are passed into a beam of high-speed electrons
Electrons knock electrons off the species and generate positive ions
Applied field accelerates ions into a magnetic field
The accelerating ion will produce its own magnetic field and the interaction between the fields will influence the cation’s path
Change in path is dependent on the mass of the cation– allowing for separation of ions of different sizes
A detector plate records where ions hit relative to each other, allowing for everyone accurate relative masses
The mole
The number of carbon atoms present in 12 g of carbon-12
Avagadro’s number
6.02*10^23 atoms = 1 mole
