Basics
What is the difference between hypothesis, theory, and law?
Hypothesis - educated guess
Theory - a statement that can be proved and can be tested.
Law - an explanation of why natural occurrences happen under specific conditions.
What are the units for atomic mass?
grams / mol
When naming acids, what is the nomenclature for an acid using perchlorate? and using chlorite?
for polyatomic ions ending in -ate, like perchlorate, the acid's name ends in -ic.
for polyatomic ions ending in -ite, like chlorite, the acid's name ends in -ous.
perchloric acid, chlorous acid
When is w positive or negative?
W will be positive when work is done ON the system by the environment.
W will be negative when work is done BY the system on the environment.
How do you find Zeff for Sulfur?
Z - S
Z = # of protons
S = (#valence electrons(0.35)) + (#core electrons(0.85))
16 - ((6*0.35)+(10*0.85))
16 - 10.6 = 5.4
Pure substances consist of ______ and _______. Mixtures can be either __________ or _______ depending on their compositions.
element, compounds. heterogeneous, homogeneous.
What is the formula for density?
Density = mass/volume
How do you know if a chemical reaction is balanced?
You have the same number of reactants and products
Convert 37ºC to Kelvin.
37ºC + 273.15 = 310.15ºK
What is the trend in the periodic table for electronegativity?
↗
The more to the right and upwards, the higher the electronegativity.
Precision.
Precision - How close multiple measurements are to one another.
Accuracy - How close a measurement is to the true value.
What is the formula for molarity?
molarity = moles of solute / volume of solution in L
HBr + NaOH → NaBr + H2O
If 8.4 grams of NaBr are produced, how many grams of HBr were reacted?
6.6 grams HBr!
g NaBr / molar mass NaBr * ratio * molar mass HBr = g HBr
What is the ideal gas law formula?
PV=nRT
What is the electron configuration for Phosphorus(15)?
1s² 2s² 2p⁶ 3s² 3p³
What are the three laws of Dalton's atomic theory?
1. Law of conservation of mass - mass is not created or destroyed.
2. Law of definite proportions - the proportions of a compound will always be the same regardless of the amount.
3. Law of multiple proportions - when two elements combine to form a compound, the masses should exist in whole number ratios.
What are the SI units for length, mass, time, temperature?
length - meter
mass - kg
time - second
termperature - kelvin
Mg + 2 HBr → MgBr2 + H2
If 119.5 grams of Mg are reacted with 12.70 grams of HBr, how many grams of MgBr2 will be produced?
14.45 g MgBr2. HBr is the limiting reagent.
What is 1 atm in torr? and in mmHg?
1 atm = 760 torr = 760 mmHg
Draw the Lewis structure for NH3 and indicate the molecular geometry.
Molecular geometry is trigonal pyramidal.
What are all all all all all of the rules of significant figures?
1. non-zeros ARE significant
2. sandwiched zeros ARE significant
3. leading zeros ARE NEVER significant
4. tailing zeros after the decimal point ARE significant
5. tailing zeros before decimal point ARE NOT significant (they can be sometimes)
6. in scientific notation, only the digits count. DONT count the "x10^3" part as sigfigs.
What is Avogadro's number?
6.022*10^23
Calculate the concentration of an HCl solution if 25.00 mL HCl is titrated with 2.000 M NaOH. The initial buret reading is 2.17 mL, and the final buret reading is 39.42 mL.
The volume of NaOH solution used is 39.42 mL − 2.17 mL = 37.25 mL.
37.25 mL NaOH((1 L)/(1000 mL))((2.000 mol NaOH)/(1 L NaOH))((1 mol HCl)/(1 mol NaOH))=0.07450 mol HCl
Calculate the wavelength of light that corresponds to a frequency of 7.30 × 1014 per second. Report your answer in units of nanometers.
1 m = 10^9 nm
vλ=c --> λ=c/ν
λ=c∕ν=(2.998×10^8 m/s)/(7.30×10^14 s^(-1) )=4.11×10^(-7) m
4.11×10^(-7) m×(1×10^9 nm)/(1 m)=411 nm
Explain.
1. Pauli Exclusion Principle
2. Aufbau Principle
3. Hund's Rule
1. Pauli Exclusion Principle - no two electrons in the same atom can have the same four quantum numbers.
2. Aufbau Principle - fill the subshells from the lowest energy upward.
3. Hund's Rule - electrons within a given subshell remains as unpaired as possible.