4.1: identify a substance as non-, strong, or weak and electrolyte, acid, or base. 1.) Identify the following compounds as electrolytes (E), acids (A), or bases (B). Also, say whether they are is “strong” (S), “weak” (W), or “non-“ (N)
S, W, or N E, A, or B
a.) H3PO4 W A
b.) HBr S A
c.) NaOH S B
d.) CaBr2 S E
e.) CH3COOH W A
f.) HNO3 S A
g.) KOH S B
h.) HF W A
i.) AgBr W E
4.2: determine the balanced net-ionic equation for an aqueous reaction.
2.) Determine the products of the following reaction and their solubility then determine the net ionic equation.
HNO3(aq) + Ca(OH)2(aq) H2O(l) + Ca(NO3)2(aq)
Ionic equation: H+(aq) + NO3-(aq) + Ca2+(aq) + 2 OH
-(aq) H2O(l) + Ca2+(aq) + NO3-(aq)
Net ionic equation: H+(aq) + 2 OH
-(aq) H2O(l)
3.) Circle the compound below that are soluble in water at room temperature: NH4OH CuS FeSO4 PbCl2 Ca(NO3)2 K2CO3
4.3: determine the oxidation number for elements in a reaction to find which elements/molecules are being oxidized and which reduced.
4.) Determine the oxidation number of the underlined element in the following compounds and molecules. Don’t’ forget the sign (+ or -)
a.) NO3- +5 b.) H2 0 c.) Br2(SO4) +1 d.) P2O5 +5
5.) Identify the ion being oxidized and the ion being reduced in the following reactions by their change in oxidation number. SHOW YOUR WORK
a.) Cr2O3(s) + 2 Al(s) ----> 2 Cr(s) + Al2O3(s) Cr: +3 0 Al: 0 +3 OIL RIG
b.) P4O10(s) + 6 H2O(l) 4 H3PO4(aq) NO OXIDATION/REDUCTION
4.4: convert between mass, moles, volume, and number of particles using Molarity.
6.) a.) Calculate the molarities of 1.055 grams of barium sulfate in 550 milliliters of water. 0.004522 mol/0.55 L = 0.0082 M
4.5: perform dilution calculations.
7.) The volume of distilled water that should be added to 50.0 mL of 3.00 M HCl(aq) in order to prepare a 0.100 M HCl(aq) solution is approximately…
50.0 x 3.00 = total volume x 0.100 total volume = 1500 mL Volume to add to 50 ml to achieve 1500ml = 1450 mL
8.) A 100.0 mL sample of 0.30 M KOH is added to 80.0 mL of 0.05 M Ba(OH)2. What is the molar concentration of OH¯(aq) in the resulting solution? (Assume that the volumes are additive)
0.1 L KOH (0.30 mol/1L) = 0.03 mol OH- from KOH
0.08 L BaOH2 (0.05 mol/1L) (2 mole /1mole BaOH2) = 0.008 mole OH-Total moles OH- = 0.03 + 0.008 = 0.038 moles
Total volume = 0.1 L + 0.08 L = 0.18 L
Molarity in mixture = 0.038 mol / 0.18 L = 0.21 M
OH-5.1: Use the first law of thermodynamics to explain and calculate system energy exchanges for physical processes (calorimetry, phase change, and expanding gases.)
9.) Calculate the amount of energy lost or gained for the following processes:
a.) A system absorbs 5 kJ of heat from the surroundings and does 116 kJ of work on the surroundings.
+5 kj – 116 kj = -111 kj = EΔ
b.) A system releases 404 kJ of heat while doing 23.2 kJ of work on the surroundings. -404 kj – 23.2kj = -428 kj
10.) Calculate the final temperature of the mixture when 4.5 grams of ethanol at a temperature of 42°C is poured into an insulated calorimeter containing 300 mL of water at 25 °C (Cs of water = 4.18 J/°C·g. Cs of ethanol is 2.46 J/°C·g)
5.2: Use the first law of thermodynamics and reaction enthalpies ( H) to explainΔ and calculate system energy changes for chemical processes.
11.) The average person is supposed to consume under 2000 Calories of energy in a day according to the FDA’s recommended diet. Calculate how much energy this is in joules. 2000 Cal (1000 cal / 1 Cal) (4.18 J / 1 cal) = 8.36 x 106
12.) If 0.8 grams of HI is decomposed according to the following reaction; give the quantity of energy released or absorbed in units of Calories
2HI(g) H2(g) + I2(g) ΔH = + 11.3 kJ
5.3: Apply Hess’s Law to calculate the missing enthalpy in a series of reactions. 13.) Find the H for the reaction below, given the following reactions and Δ
subsequent H values: Δ
PCl5(g) → PCl3(g) + Cl2(g) ΔH = ?
P4(s) + 6Cl2(g) → 4PCl3(g) ΔH = -2439 kJ 4PCl5(g) → P4(s) + 10Cl 2(g) ΔH = 3438 kJ To make the third equation:
Multiply the first equation by 4 (so the first enthalpy would be x4)
Reverse the second equation (so the sign of the second enthalpy is reversed to positive)
So the Hess’s law equation is: (4 x ?) + (+2439 kj) = 3438 kj Algebra says… ΔH = ? = 249.8 kj
5.4: Calculate how the enthalpy changes ( H) for a given reaction based on Δ Heats of formation.
14.) Calculate the heat of reaction for the following reaction. 2 H2S(g) + 3 O2(g) 2 H2O(l) + 2 SO2(g) ΔHrxn = ?
H Δ f
H2S(g) -20.1 kj [(2 x -241.8 kj) + (2 x -296.1 kj)] – [(2 x -20.1) + 0] =
H2O(g) -241.8 kj -1036 kj
SO2(g) -296.1 kj
6.1: Calculate the energy, wavelength, speed, and/or frequency of electromagnetic photons.
15.) A photoelectric array requires 6.23 x 104 joules of radiant light energy to strike it in order to trigger an electric switch circuit. If 524 nm wavelength light is shining on the photoelectric array, how many total photons of light will be required to trigger the electric switch?
524 nm (1 m /109 nm) = 5.24 x 10-7 m Wavelength x Freq = speed of light
3.00 x 108 m/s / 5.24 x 10-7 m = freq = 5.725 x 1014 Hz
E = freq x plancks constant = 5.725 x 1014 Hz x 6.626 x 10-34 = 3.79 x 10-19 J = E of 1 photon
Total energy / energy of 1 photon = # of photons = 6.23 x 104 J / 3.79 x 10-19 J = 1.64 x 1023 photons
6.2: Calculate and interpret line spectra for identification of elements.
16.) An electron of a hydrogen atom moves from the n=6 to the n=2 principal energy level.
a.) Calculate the wavelength of the associated photon of light. 1/ = 1.097 x 10λ 7 (1/22 – 1/62) = 2.437 x 106
= 1/2.437 x 10
Λ 6 = 4.10 x 10-7 m
b.) Is the electron in this example moving closer to the nucleus or further away? Closer (higher energy level to a lower one)
c.) Is the electron in this example absorbing or emitting a photon of light?
6.3: Compare the electron arrangements of historic electron models and the modern quantum mechanical electron cloud models.
17.) Draw a picture model of the electron structure of a sodium atom using both a Bohr model and a quantum mechanical model. For the quantum mechanical model show the shape of the orbitals and how many electrons go in each.
Bohr Model Quantum Mechanical Model
18.) How did the Heisenburg Uncertainty Principle changed previously existing model (the Bohr model) of electron structure in the atom?
The HUP said that you cannot know the location and momentum of an electron simultaneously and thus Bohr’s model that depicted electrons in specific locations and with specific orbiting momentums was incomplete. The HUP basically says that you can only know the general area (orbitals) in which electrons should be found and not their specific location due to wave mechanic properties dominating particle mechanic properties.
6.4: Write and/or illustrate the bohr model, electron configuration, or orbital diagram for an element using quantum mechanical rules (Hund’s and Pauli.)
19.) Give the full (not abbreviated) electron configuration, the number of valence electrons, and the possible Aufbau diagram for the valence electrons for each element.
Element Electron Configuration Valence Electrons Aufbau diagram
Example:
O 1s22s22p4 6 v e
Argon 8 ve
Rubidium See next page…
20.) Briefly explain the difference between energy levels, subshells, orbitals, and spin states. It may be necessary to define one in relationship to another. It may also help to draw diagrams.
Energy Levels: Distance from nucleus. Higher energy levels mean further out from nucleus.
Sublevels: A collection of orbitals of a certain shape within a given energy level.
Orbitals: the 3-d spaces where up to 2 electrons can be found.
