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)