Dimensional Analysis
How much does 15.0 cm3 of aluminum weigh? The density of aluminum is 2.70 g/cm3 .
40.5 grams
A sample of groundwater from coastal South Carolina contains 7.73% 6Li (6.015123 u) and 92.27% 7Li (7.016003 u). What is the average atomic mass of lithium in the sample? Round to 3 sig figs.
6.94 u
Which has greater effective nuclear charge: O or S? Explain.
O because it feels more attraction to the protons in the nucleus than Sulfur does. Sulfur has more orbitals and thus more electrons which repel each other (shielding).
What are the SI units of the following: length, mass, time, electrical current, temperature, chemical amount, luminous intensity, energy?
Length → meter (m)
Mass → kilogram (kg)
Time → second (s)
Electrical current → ampere (A)
Temperature → kelvin (K)
Amount of substance → mole (mol)
Luminous intensity → candela (cd)
Energy → joule (J) = kg·m²·s⁻²
What is the difference between ions and isotopes?
Ions differ in electrons and have a different charge as a result.
Isotopes differ in neutrons and have a different atomic weight.
We are currently moving toward Los Angeles at the rate of 0.020 m/year. At this rate, how long will it take us to reach L.A., 640 km away?
3.2 x 107 years. (2 sig fig)
Write the condensed electron configuration for Silver (Ag).
[Kr]5s14d10
A hydrogen atom absorbs a photon and an electron jumps from n=2 to n=6. What is the energy difference?
4.84 × 10−19 J per photon
What are the symbols and values of the following prefixes: giga-, mega-, kilo-, centi-, milli-, micro-, nano-, pico-?
giga- G 109
mega- M 106
kilo- k 103
centi- 10−2
milli- m 10−3
micro- µ 10−6
nano- n 10−9
pico- p 10−12
What is the Pauli Exclusion Principle and what is Hund's Rule?
Pauli Exclusion Principle → No two electrons can have the same quantum numbers (max 2 electrons per orbital, opposite spins).
Hund's Rule → Electrons spread out in equal-energy orbitals with parallel spins before pairing.
How fast in miles per hour is 200 m/s? (1 km = 0.62137 mi) (3600 sec = 1 hr)
447 miles/hour
How many O2 molecules are in 0.250 mol of O₂?
1.51 x 1023 O2 molecules
Which one of the following sets of quantum numbers is valid?
a. n = 5; l = 2; ml = 3; ms = -1/2
b. n = 5; l = 0; ml = 0; ms = +1/2
c. n = 0; l = 2; ml = 2; ms = -1/2
d. n = 5; l = 2; ml = 3; ms = +1/2
B is the only set of valid quantum numbers.
What does each quantum number describe (n, l, ml , ms)? Break l down into each sub-shell (for example what sub-shell am I in when l = 2?)
n describes size
l describes shape
ml describes orientation
ms describes electron spin/rotational motion of election
l = 0 means s sub-shell
l = 1 means p sub-shell
l = 2 means d sub-shell
l = 3 means f sub-shell
ml can have whole # values between l and -l
Which of the following are intensive properties of a sample of a substance?
A. freezing point; B. volume; C. temperature
A and C are intensive properties because they do not depend on the amount of substance present in the sample.
The relationship between electric power (P), current (I) and voltage (V) is given by P=IV. I is in amps, V is in volts; therefore P is in amp⋅volts. A more common unit of power is the watt: 1 watt = 1 amp⋅volt. Ordinary house current is 120 volts. How many amps of current are drawn by a 60 watt light bulb?
0.5 amp
How many moles of O2- are in 0.55 mol of Al2O3? What is the mass in grams of the O2- ions?
Moles of O²⁻: 1.7 mol
Mass of O²⁻ ions: 26 g
Calculate the frequency of the photons emitted by hydrogen atoms when they undergo n=5 to n=3 transitions. Is this in the visible region of the electromagnetic spectrum? Is the photon emitted or absorbed?
f = 2.34 x 1014 Hz
No, it's in the infrared region of the EMS (Wavelength = 1282 nm)
Photon is emitted
Briefly summarize each of the following experiments (i.e. how was it set up and what is the takeaway of the experiment?): Thomson’s Cathode Ray Experiment, Millikan’s Oil Drop Experiment, Rutherford’s Gold Foil Experiment.
Thomson's Cathode Ray: Thomson used a cathode ray tube (with electrically charged plates) to determine that electrons exist and the cathode rays must consist of tiny negative particles. He also determined the charge to mass ratio of electrons.
Millikan's Oil Drop: Millikan used oil droplets, gave them a negative charge with an X-Ray and suspended the droplet between two plates. From this he determined the charge of electrons. He also calculated the mass of electrons from Thomson's data.
Rutherford Gold Foil: A thin sheet of gold foil was bombarded with alpha particles. A fluorescent screen around the foil detected where the alpha particles went. This determined that the nucleus was dense and made up of "massive" positively-charged particles.
Below are measurements students made in the lab. Which student's data is most accurate? Which student's data is most precise?
Student 1: 183.5°C, 185.9°C, 184.6°C
Student 2: 190.0°C, 183.3°C, 187.1°C
Student 3: 181.2°C, 182.0°C, 181.7°C
Accepted value: 185°C
Student 1 has the most accurate data.
Student 3 has the most precise data.