Chemistry Class 1 & 2
How many electrons does F- have?
10
What bond angle to sp3 carbons have?
109.5
What bond angle do sp2 carbons have?
120
What bond angle do sp carbons have?
180
How many electrons are found in π bonds in acetylene (C2H2)? A. 4 B. 0 C. 6 D. 2
A. 4
Sodium dodecyl sulfate, also known as SDS, is a common denaturation agent used while separating proteins via gel electrophoresis. It is composed of a highly charged head and a long hydrocarbon tail. Given application of SDS to a protein increases its solubility in water, what forces are responsible for association of SDS with the protein of interest? A. Dipole-dipole forces B. Hydrogen bonding C. Ion-dipole forces D. London dispersion forces
A. Dipole-dipole forces
In organic solution, F- deprotonates dissolved HCl. Which of the following explains this observation? A. F- has a smaller radius than Cl-. B. F- is a stronger acid than Cl-. C. F- has a greater electronegativity than Cl-. D. F- has a lower ionization energy than Cl-.
A. F- has a smaller radius than Cl-. F- is much less stable than Cl- so fluorine will outcompete for the hydrogen.
Which of the following molecules has the lowest boiling point? A. F2 B. Cl2 C. H2O D. HCN
A. F2 This is a question asking about intermolecular forces. Florine is smaller than chloride. Amongst all the choices it interacts via London dispersion forces which is the weakest bonding
Which pair of liquids below will be immiscible? A. H2O and CCl4 B. CH3OH and CH3CH2OH C. CH3CH2CH2CH2CH3 and CH3CH2CH2CH2Br D. CCl4 and C6H6
A. H2O and CCl4 A solvent pair will be made of polar and nonpolar compounds. Molecules with very different intermolecular forces.
Which of the following compounds would exhibit the strongest intermolecular forces? A. CO2 B. CHCl3 C. CH3CO2H D. C6H14
C. CH3CO2H Hydrogen bonding is the strongest type of intermolecular forces!
Which of the following pairs will have the strongest intermolecular forces between them? A. O2 and N2 B. HCl and CHCl3 C. NaCl and NH3 D. H2O and C8H18
C. NaCl and NH3
Which of the following orbitals is NOT found in the carbon-carbon bonds of propene? A. Pure p orbitals B. sp3 hybrid orbitals C. Pure s orbitals D. sp2 hybrid orbitals
C. Pure s orbitals
What are the colors of the rainbow?
ROYGBV
What is the trend for radius?
Radius increases as the periodic table goes down and to the left.
When deciding what the best resonance structure is, how does electronegativity play a role?
The more electronegative atom should have the formal negative charge.
A positive H and a negative S will always be __________ regardless of temperature
nonspontaneous
Which of the following is the most stable ionization state for Sn? A. Sn+1 B. Sn+3 C. Sn+4 D. Sn+2
D. Sn+2
What is the mass number?
P + N
Which of the following lists hydrogen halides in terms of increasing standard heats of formation? A. HF < HBr < HCl < HI B. HI < HBr < HCl < HF C. HBr < HF < HCl < HI D. HF < HI < HCl < HBr
A. HF < HBr < HCl < HI HF is going to be the lowest because it is the most electronegative and the smallest, therefore it will be the most stable and lower heat of formation. HI is actually endothermic
Each of the following pairs of substances interact through van der Waals forces EXCEPT: A. Na+ and H2O B. HCl and Ar C. Cl2 and Br2 D. NH3 and H2S
A. Na+ and H2O Sodium is not neutral
A reaction occurs that results in a set of products with more stable bonds and more orderly arrangement than were present in the reactants. Which of the following is true of this reaction? A. The enthalpy and entropy changes are negative. B. The enthalpy change is positive, and the entropy change is negative. C. The enthalpy change is negative, and the entropy change is positive. D. The enthalpy and entropy changes are positive.
A. The enthalpy and entropy changes are negative. In order for to create more stable bonds, enthalpy must be negative because this requires the loss of energy
The reactivity of alkali metals follows the trend Cs > Rb > K > Na > Li. Which of the following is the best explanation for this trend? A. The ionization energy increases from Cs to Li. B. The electron affinity increases from Li to Cs. C. The electronegativity decreases from Cs to Li. D. The atomic size decreases from Li to Cs.
A. The ionization energy increases from Cs to Li.
If an atom's atomic number equals its atomic weight, which of the following would be true? A. The number of protons equals the number of electrons. B. The number of neutrons equals the number of protons. C. The number of neutrons equals the number of electrons. D. The number of protons is less than the number of neutrons.
A. The number of protons equals the number of electrons. The only way this happens is if there are no neutrons
A substance has a standard heat of formation of 0. This is best explained by which of the following statements? A. The substance is an element in its standard state. B. At low temperatures, entropy makes virtually no contribution to changes in Gibbs free energy. C. ΔH is a state function. D. The bond energies within the substance are very negative.
A. The substance is an element in its standard state.
Which of the following is the correct electron configuration for the iron ions present in rust, Fe2O3? A. [Ar] 3d5 B. [Ar] 4s23d3 C. [Ar] 4s23d4 D. [Ar] 3d6
A. [Ar] 3d5 This is because oxygen will always have a -2 charge. In order to equal out the three oxygen atoms iron will have to have a +3 charge. Iron loses three electrons giving it the above configuration.
According to the laws of thermodynamics, an endothermic reaction is most likely to be spontaneous if the: A. change in entropy is positive and the temperature is high. B. change in entropy is negligible and the temperature is low. C. change in entropy is positive and the temperature is low. D. change in entropy is negative and the temperature is high.
A. change in entropy is positive and the temperature is high.
Compared to carbon, nitrogen has a: A. greater ionization energy and more negative electron affinity. B. smaller ionization energy and more positive electron affinity. C. smaller ionization energy and more negative electron affinity. D. greater ionization energy and more positive electron affinity.
A. greater ionization energy and more negative electron affinity.
What is the trend of electron affinity?
Affinity becomes more negative the farther to the right of the periodic table. This also means more favorable.
Why does the radius decrease from right to left?
As there is an increase in nuclear charge, the nucleus pulls the electrons in tighter resulting in a decreased radius.
How many electrons are shared in the bond between sodium and chlorine in a molecule of NaCl? A. 1 B. 0 C. 2 D. 3
B. 0 No electrons are shared in ionic bonds
Rank the average C—O bond length from shortest to longest for CO, CO2, and CO32-. A. CO32- < CO2 < CO B. CO < CO2 < CO32- C. CO32- < CO < CO2 D. CO < CO32- < CO2
B. CO < CO2 < CO32-
Which of the following molecules has the greatest dipole moment? A. SO3 B. H2O C. SiCl4 D. CO2
B. H2O
Metal-organic frameworks (MOFs) are systems of metals tethered together by organic linkers forming porous solids with exposed, active metal centers. MOFs are often used to bind and hold gases such as H2, often allowing for a more dense packing of gas than allowed in the pure liquid state. If the binding of gas to metals in the MOF is spontaneous, which must be true? A. The enthalpy of binding is positive. B. The enthalpy of binding is negative. C. The change in free energy associated with binding is positive. D. The entropy of reaction is positive.
B. The enthalpy of binding is negative. Entropy is negative because disorder is decreased from gas to solid. If this is true, enthalpy must be negative.
Which of the following describes the orbital geometry of an sp2 hybridized atom? A. Tetrahedral B. Trigonal planar C. Bent D. Linear
B. Trigonal planar
A sample of excited hydrogen atoms emits a light spectrum of specific, characteristic wavelengths. The light spectrum is a result of: A. energy released as H atoms form H2 molecules. B. the light wavelengths which are not absorbed by valence electrons when white light is passed through the sample. C. excited electrons dropping to lower energy levels. D. particles being emitted as the hydrogen nuclei decay.
C. excited electrons dropping to lower energy levels.
At 298 K, ?H° = 436 kJ and ?S° = 100 J/K for the reaction H2(g) 2 H(g). Therefore, this reaction: A. is at equilibrium at 298 K. B. is spontaneous at 298 K. C. is not spontaneous at 298 K but will be spontaneous at high enough temperatures. D. will never be spontaneous, regardless of the temperature.
C. is not spontaneous at 298 K but will be spontaneous at high enough temperatures.
At STP, a certain liquid will spontaneously vaporize, even though the reaction is endothermic. The most likely explanation for this is that: A. change in enthalpy has no effect on reaction spontaneity. B. temperature has no effect on reaction spontaneity. C. this reaction results in an increase in entropy. D. endothermic reactions are always spontaneous.
C. this reaction results in an increase in entropy.
When a sample of solid NH4NO3 is dissolved in water, the reaction flask becomes cold to the touch. What can be concluded about the given thermodynamic values for the solvation process? A. ΔG < 0, ΔH < 0, ΔS > 0 B. ΔG > 0, ΔH < 0, ΔS > 0 C. ΔG < 0, ΔH > 0, ΔS > 0 D. ΔG < 0, ΔH > 0, ΔS < 0
C. ΔG < 0, ΔH > 0, ΔS > 0 G must be negative because it is spontaneous. H is positive because it is an endothermic reaction - the flask becomes cold. S must be positive in order for the G to be negative and because we are going from a solid to a gas.
Combustion of methane
CH4 + 2O2 -> CO2 + 2H2O
Which of the following electron transitions (between energy levels, labeled by n) could account for the emission of photons of red, yellow, and blue light from a pure noble gas? A. n = 4 to n = 1, n = 4 to n = 2, and n = 4 to n = 3, respectively B. n = 1 to n = 0, n = 2 to n = 1, and n = 3 to n = 2, respectively C. n = 2 to n = 1, n = 3 to n = 2, and n = 4 to n = 3, respectively D. n = 4 to n = 3, n = 3 to n = 2, and n = 2 to n = 1, respectively
D. n = 4 to n = 3, n = 3 to n = 2, and n = 2 to n = 1, respectively Red is the lowest energy and moving from n=4 to n=3 will require the least amount of energy.
Which of the following reactions has the most positive ∆Srxn? A. C(diamond) C(graphite) B. 6 H2O(g) 6 H2O(l) C. 6 CO2(g) + 6 H2O(g) C6H12O6(s) D. CO2(s) CO2(g)
D. CO2(s) CO2(g) Solid to a gas
In the formation of a bond, what dictates the distance between the two atoms? A. Distance with maximal electron cloud overlap B. Distance with minimal electron cloud overlap C. Distance at which maximal potential energy is obtained D. Distance at which attractive and repulsive forces are equal
D. Distance at which attractive and repulsive forces are equal
Given the same number of moles, which of the following solids will have the lowest melting point? A. SiO2 B. Cu C. NaI D. H2Se
D. H2Se Consists of dipole-dipole, which is weaker than covalent bonding, and ionic forces.
Which of the following molecules contains the most polar covalent bond? A. CH4 B. H2O C. NaCl D. HF
D. HF Electronegativity
The vapor pressure of Liquid I is greater than the vapor pressure of Liquid II. Which of the following is true about Liquid I? A. It has stronger intermolecular forces than does Liquid II. B. It has a higher heat of fusion than does Liquid II. C. It has a higher heat of vaporization than does Liquid II. D. It boils at a lower temperature than does Liquid II.
D. It boils at a lower temperature than does Liquid II.
Which of the following is true of an electron in an excited state? A. It has absorbed a photon, and its energy has decreased. B. It has emitted a photon, and its energy has increased. C. It has emitted a photon, and its energy has decreased. D. It has absorbed a photon, and its energy has increased.
D. It has absorbed a photon, and its energy has increased.
Question 7 Rank the following elements and ions from least to greatest atomic radius: S, S+, P, P-, P2- A. S < S+ < P < P- < P2- B. P2- < P- < P < S < S+ C. S < P < S+ < P- < P2- D. S+ < S < P < P- < P2-
D. S+ < S < P < P- < P2- Anions will always have a greater radius. Cations have a smaller radius because the remaining valence electrons are experiencing a stronger effective nuclear charge.
Perspiration is important in maintaining normal body temperature. Compared to water at its boiling point, which of the following is true about water at normal human body temperature? A. Intermolecular forces are weaker B. Average kinetic energy is greater C. More energy is required for gas expansion D. The heat required for vaporization is higher
D. The heat required for vaporization is higher The heat required to vaporize is higher at lower temperatures
CF2Cl2 is a common freon used in refrigerators. The strongest intermolecular forces holding these molecules together are: A. ionic forces. B. hydrogen bonding. C. London dispersion forces. D. dipole-dipole forces.
D. dipole-dipole forces. This is a better answer than London dispersion forces because the molecule is slightly polar
Compared to the atomic radius of S, the atomic radius of Al is: A. smaller, due to decreased nuclear charge. B. smaller, due to increased nuclear charge. C. larger, due to increased nuclear charge. D. larger, due to decreased nuclear charge.
D. larger, due to decreased nuclear charge.
What is higher energy, gamma or radio waves?
Gamma are the highest, radio are the lowest
The second ionization energy is always _________ than the first because electrons are more tightly bound after one is displaced
Greater
The strongest intermolecular forces occur between molecules with a _________ magnitude of charge.
Greater
What is the relationship between wavelength and photon energy?
Inverse
What do the number of neutrons determine?
Isoptopes
The compound with the ______ vapor pressure has the strongest intermolecular forces.
Least
What types of molecules can interact via van der Waals forces?
Neutral
If electrons are delocalized by residence do they contribute to electron hybridizations? (sp, sp2, sp3)
No, N-H with two other groups attached will be sp2 if its lone pairs are contributing to resonance.
What is the trend of ionization energy and electronegativity?
They both increase up and to the right on the periodic table. Ionization energy is the energy needed to remove the outer most electron from an atom.