practice exam 1

The energy levels for different n in the Bohr model for hydrogen have the following values: level : n = 4 energy : −82.0 kJ ∕ mol level : n = 3 energy : −145.8 kJ ∕ mol level : n = 2 energy : −328.0 kJ ∕ mol level : n = 1 energy : −1312 kJ ∕ mol In the hydrogen spectrum, what is the wavelength of light associated with the n = 3 to n = 2 transition?

657.0 nm

Which set of quantum numbers is not allowed? A. n = 0,ℓ = 0, mℓ = 0, ms = +1/2 B. n = 1,ℓ = 0, mℓ = 0, ms = −1/2 C. n = 2, ℓ = 1, mℓ = −1, ms = +1/2 D. n = 3,ℓ = 1, mℓ = 0, ms = +1/2 E. n = 4, ℓ = 3, mℓ = 3, ms = 1/2

n = 0,ℓ = 0, mℓ = 0, ms = +1/2

Determine if each of the four situations below describes kinetic or potential energy. I. bonding interaction between hydrogen and oxygen that creates a water molecule. II. water stored in a dam. III. a frisbee flying through the air. IV. thermal energy of atoms and molecules.

potential potential kinetic kinetic

The temperature rises from 25.00°C to 29.00°C when 3.50 g of sucrose (Formula C12H22O11, molar mass 342.3 g/mol) undergoes combustion in a bomb calorimeter. Calculate ΔE for the combustion of sucrose in kJ⁄mol sucrose. The heat capacity of the calorimeter is 4900 J⁄°C.

-1.92 x 10^3 kJ⁄mol

Using a Born-Haber cycle, calculate the enthalpy of formation of calcium fluoride, CaF2(s), given the following data: Ca (s) → Ca (g) +179 kJ ∕ mol Ca (g) → Ca+ (g) + e− +590 kJ ∕ mol Ca+ (g) → Ca2+ (g) + e− +1145 kJ ∕ mol F2 (g) → 2 F (g) +158 kJ ∕ mol F (g) + e−→ F− (g) −328 kJ ∕ mol Ca2+ (g) + 2 F− (g) → CaF2 (s) −2630 kJ ∕ mol

-1214 kJ ∕ mol

The combustion of methanol is described by the following equation. 2 CH3OH (l) + 3O2 (g) → 2 CO2 (g) + 4 H2O (l), ΔH = −1454 kJ Calculate delta Hf° for CH3OH(l) using the following information. delta Hf° for CO2(g) = −393 kJ ∕ mol delta Hf° for H2O(l) = −286 kJ ∕ mol

-238 kJ/mol

When 2.00 g of Ba(s) is added to 25.00 g of water in a container open to the atmosphere, the reaction shown below occurs and the temperature of the resulting solution rises from 24.38°C to 80.00°C. If the specific heat of the solution is 4.18 J⁄(g ∙ °C), calculate ΔH for the reaction, as written Ba (s) + 2 H2O (l) → Ba(OH)2 (aq) + H2 (g)

-430 kJ

The combustion of methanol is described by the following equation. 2 CH3OH (l) + 3O2 (g) → 2 CO2 (g) + 4 H2O (l), ΔH = −1454 kJ What is the enthalpy change for the combustion of 2.09 g methanol (CH3OH) in excess oxygen?

-47.4 kJ

Which of the following statements is false? A. When a gas expands, the system is doing work on the surroundings. B. Heat and work are state functions. C. Boiling of water is an endothermic process. D. Energy transfers from hotter objects to colder objects. E. In exothermic reactions, the products have lower energy than the reactants.

Heat and work are state functions.

The statement "If orbitals have the same energy (degenerate as in subshell orbitals), put one electron in each degenerate orbital before pairing" is known as:

Hund's rule

Arrange the following four electromagnetic spectral regions in order of decreasing energy. visible, X-ray, microwave, radio

X-ray, visible, microwave, radio

Which term refers to a measurement of heat transferred at constant pressure? A. change in internal energy B. specific heat capacity C. molar heat capacity D. change in enthalpy E. work of expansion

change in enthalpy

Which of the following ionic forms of V will have the most number of unpaired electrons? A. V+ B. V2+ C. V3+ D. V4+ E. V

V+

Place the following in order of increasing radius. Ca, Cl, Mg

Cl < Mg < Ca

The bond length in the BrF molecule is 178 pm and the measured dipole moment is 1.29 D (debyes). What is the magnitude of the negative charge (in units of the electronic charge e) on F in BrF? (1 debye = 3.34 x 10^−30 coulomb-meters; electronic charge = e = 1.6 x 10^−19 coulombs).

0.15

Red light has a wavelength of 6.49 x 10^2 nm. The energy of a photon of red light is

3.06 x 10^19 J

How many of the following atoms have 3 unpaired electrons? I. N II. As III. V IV. Co

4

The quantum numbers (n, ℓ, mℓ, ms) for the valence electron of a potassium atom in its ground state could be: A. 3, 0, 0, − ½ B. 3, 1, −1, + ½ C. 4, 0, 0, + ½ D. 4, 2, 1, + ½ E. 4, 1, 1, − ½

4, 0, 0, + ½

For which of the following reaction is the enthalpy change for the reaction equal to delta Hf° of the product? A. N2 (g) + 3 H2 (g) → 2 NH3 (g) B. CO (g) + ½ O2 (g) → CO2 (g) C. 2 H (g) → H2 (g) D. C (graphite) + 2 H2 (g) → CH4 (g) E. H2 (g) + Cl2 (g) → 2 HCl (g)

C (graphite) + 2 H2 (g) → CH4 (g)

A 140.0 g sample of water at 20.0 °C is mixed with 100.0 g of a certain metal at 95.0 °C. After thermal equilibrium was established, the temperature of the mixture is 24.6 °C. What is the specific heat capacity of the metal?

C. 0.38 J⁄g °C

Which of the following electron configurations for the atom in its ground state is incorrect? A. Al: [Ne] 3s2 3p1 B. Cr: [Ar] 4s2 3d4 C. As: [Ar] 4s2 3d10 4p3 D. Fe:[Ar] 4s2 3d6 E. Zn: [Ar] 4s2 3d10

Cr: [Ar] 4s2 3d4

Consider an atom traveling at 1% of the velocity of light. The de Broglie wavelength is measured to be 7.00 × 10−3 pm. Which element is this?

F

Which statement is false? A. The spin quantum number can have values of +½ or −½. B. The 4s orbitals have lower energy than the 3d orbitals (for transition metals). C. The electron density at a point is proportional to the square of the wave function 2 at that point. D. For a given value of the principal quantum number n, the angular momentum quantum number ℓcan have integer values ranging from 0 to n. E. No two electrons can have the same four quantum numbers.

For a given value of the principal quantum number n, the angular momentum quantum number ℓcan have integer values ranging from 0 to n.

The combustion of methanol is described by the following equation. 2 CH3OH (l) + 3O2 (g) → 2 CO2 (g) + 4 H2O (l), ΔH = −1454 kJ Which of the following statement(s) is (are) true? I. The reaction is endothermic. II. The enthalpy change would be different if water vapor is produced. III. The sign of work for the combustion of methanol is positive since the volume decreases in this reaction.

II and III

Which of the following orderings gives the incorrect trend in size? I.Cl < Cl− II.Na+ < Na III.C < Si IV.N < O

IV

Which of the following is a reasonable criticism of the Bohr model of the atom? A. It does not explain the spectral characteristics of hydrogen. B. It does not account for the existence of line spectra. C. It requires that the energy levels of the electron in the atom be quantized. D. It implies that a one electron system can have several colors of light in its line spectrum. E. It does not work for multielectron atoms.

It does not work for multielectron atoms.

Place the following ionic compounds in order from lowest to highest lattice energies. NaCl KCl CaO MgO AlP

KCl < NaCl < CaO < MgO < AlP

Place the following in order of increasing radius. F−, Mg2+, O2−

Mg2⁺ < F⁻ < O2⁻

Which of these statements is false? A. Atomic radius increases on going down a group. B. Second ionization energies are smaller than first ionization energies. C. A negative ion is larger than its parent neutral atom. D. Valence electrons are easier to remove than core electrons. E. Ionization energies increase on going from left to right across a period.

Second ionization energies are smaller than first ionization energies.

Which statement is true? A. The 3d orbitals have lower energy than the 3p orbitals. B. The 4p orbitals can hold more electrons than the 3d orbitals. C. The p subshell has 5 (degenerate) orbitals. D. Two electrons in the 1s orbital will have the same spin. E. The 2p orbitals hold up to 6 electrons.

The 2p orbitals hold up to 6 electrons.

Which of the following statements is true? A. The freezing of rain drops is an example of an exothermic reaction. B. Ice has a higher specific heat capacity than liquid water. C. A bomb calorimeter measures ∆H directly. D. Internal energy and enthalpy are not state functions. E. If heat is released in a reaction, the reaction is endothermic.

The freezing of rain drops is an example of an exothermic reaction.

Two metals of equal mass with different specific heat capacities are subjected to the same amount of heat. Which undergoes the smaller change in temperature? A. The metal with the higher specific heat capacity. B. The metal with the lower specific heat capacity. C. Both undergo the same change in temperature. D. You need to know the initial temperatures of the metals.

The metal with the higher specific heat capacity.

Which of the following signs on q and w represent a system that is doing work on the surroundings, and gaining heat from the surroundings? A. q is positive, w is positive B. q is positive, w is negative C. q is negative, w is positive D. q is negative, w is negative

q is positive, w is negative

Which word or phrase least applies to the quantum number represented by the symbol n?

shape

Which of these elements have the smallest and largest first ionization energies: Ca, F, Mg, N, P?

smallest Ca, largest F

In an experiment searching for the photoelectric effect, an incident beam of green light did not eject any electrons from a metal. In order to eject electrons, the experimenter should

try blue light.

Carbon monoxide (CO) is a highly poisonous gas. Write the equation that represents the standard molar enthalpy of formation (delta Hf°)for CO. Then, using the following data, calculate delta Hf° of CO (g). C(graphite) + O2(g) → CO2(g) ΔH°= −394.0 kJ 2 CO(g) + O2(g) → 2 CO2(g) ΔH°= −566.0 kJ

−111.0 kJ ∕ mol

At 298 K, the following heats of reaction are known: S (s) + O2 (g) → SO2 (g) ΔH = −296.1 kJ 2 SO3 (g) → 2 SO2 (g) + O2 (g) ΔH = 198.2 kJ Calculate ΔH for the reaction 2 S (s) + 3 O2 (g) → 2 SO3 (g) at 298 K.

−790.4 kJ