Chemistry Subject Review Flashcards
The pKa values for the following vitamins are given in the table.
What is the Ka value for niacin at 25°C?
a. 5.1 x 10^-4
b. 1.6 x 10^-3
c. 2.2 x 10^-3
d. 6.2 x 10^2
b. 1.6 x 10^-3
pKa = -log10Ka
Which of these molecular formulas represents a strong base when dissolved in water?
a. Ca(OH)2
b. CH3COOH
c. HNO3
d. NH3
a. Ca(OH)2
What best describes the intermolecular forces that most contribute to the increased boiling point of pure CCl4 (76.72°C) compared to CHCl3 (61.2°C)?
a. The extra chlorine atom makes CCl4 more polar.
b. The hydrogen bonding capacity of CHCl3 is weakened by electron shielding.
c. The extra electrons in CCl4 provide a greater surface area for London dispersion forces.
d. The symmetry of CCl4 increases the London dispersion forces.
e. The polar bond of CHCl3 inhibits van der Waals forces present in the non-o= to an increase in intermolecular forces compared to CCl4.
c. The extra electrons in CCl4 provide a greater surface area for London dispersion forces.
What reaction involves two water molecules forming hydronium and hydroxide ions?
a. Double replacement
b. Hydrolysis
c. Self-ionization
d. Synthesis
c. Self-ionization
_____ oxides are acidic in nature, and _____ oxides are basic in nature.
a. Amphoteric, neutral
b. Neutral, amphoteric
c. Nonmetallic, metallic
d. Metallic, non-metallic
c. Nonmetallic, metallic
0.105 mol of argon and 0.0150 mol of bromine gas are held in a 5 L flask, at 25°C. If the overall pressure of the flask is 447 mm Hg, what is the partial pressure of each gas?
a. Argon 105 mm Hg; bromine 342 mm Hg
b. Argon 100 mm Hg; bromine 340 mm Hg
c. Argon 342 mm Hg; bromine 105 mm Hg
d. Argon 391 mm Hg; bromine 55.9 mm Hg
e. Argon 390 mm Hg; bromine 56 mm Hg
d. Argon 391 mm Hg; bromine 55.9 mm Hg
The first step is to determine the mole fraction of each gas, x.
xAr = 0.105/(0.105 + 0.0150) = 0.875
xBr = 0.0105/(0.105 + 0.0150) = 0.125
Next, determine the partial pressure of each gas using Dalton’s law, pi = P*xi
pAr = 4470.875 = 391 mm Hg
pBr = 4470.125 = 55.9 mm Hg
What is stoichiometry?
a. The branch of chemistry that shows the quantitative relationship between reactants and products
b. The branch of chemistry that shows the qualitative relationship between reactants and products
c. An analytical technique used to separate and identify ionized molecules
d. A process for taking electrical measurements
a. The branch of chemistry that shows the quantitative relationship between reactants and products
Identify the lowest-energy Lewis structure among the 3 resonance states of (1) cyanate and (2) fulminate. What is the formal charge of (a) nitrogen in cyanate and (b) carbon in fulminate when they are in their lowest energy resonance form? Refer to the image.
a. (a) 0 (b) -2
b. (a) -1 (b) -2
c. (a) -1 (b) -1
d. (a) 0 (b) -1
e. (a) -2 (b) -2
c. (a) -1 (b) -1
The rate r of a zero-order reaction A→B can be expressed in which form?
a. r = k
b. r = k [A]
c. r = k ln [A]
d. r = k [A]^2
e. r = k [A]^1/2
a. r = k
Which would be expected to have the shortest bond length?
a. C-N in acetonitrile
b. C-O in acetone
c. C-C in acetylene
d. C-C in benzene
a. C-N in acetonitrile
In the reaction between a methyl cation and ethanol to yield methoxymethane, which reactant is considered the Lewis acid?
a. Ethanol
b. Methyl cation
c. Both reactants are Lewis acids.
d. Neither reactant is a Lewis acid.
e. Lewis acids/bases cannot be applied to this reaction.
b. Methyl cation
A table of elements and their electronegativity values are given below.
Which compounds are ionic?
a. B2O3 and Na2O
b. CH4 and NaF
c. H2 and CO
d. NaF and Na2O
d. NaF and Na2O
Case:
To standardize an unknown solution of sodium thiosulfate, Na2S2O3, a group of students prepares a standard solution of potassium iodate, KIO3. Before the titration, the KIO3 solution must be reacted with excess potassium iodide, KI, to form a colorless solution containing triiodide, I3-. This process goes through an intermediate reaction first forming I2, then excess iodide further reacts with the iodine to form I3-. Starch is then added to the triiodide solution as an indicator before the titration of Na2S2O3.
Question:
What is the ratio of iodine atoms to iodate in the balanced equation for the redox reaction required to form iodine (I2) from iodate and iodide (before the reaction to form triiodide)?
a. 1:1
b. 2:1
c. 3:1
d. 5:1
e. 6:1
d. 5:1
Molecular oxygen, O2, in group VI of the periodic table, is attracted by strong magnetic fields in its liquid state (gases are too diffuse). This attraction is a result of the molecule having unpaired electron(s), a phenomenon called paramagnetism. The valence bond theory, however, describes this molecule as having a double bond and 2 sets of lone pairs that are spin paired (diamagnetic).
How would the experimental observations be reconciled by describing the electron configuration of O2 using the molecular orbital theory?
a. (σ2s)2 (σ2s)2 (σ2p)2 (π2p)2 (π2p)2 (σ*2p)2
b. (σ2s)2 (σ2s)2 (σ2p)2 (σ2p)2 (π2p)2 (π2p)1 (π*2p)1
c. (σ2s)2 (σ2s)2 (σ2p)2 (π2p)2 (π2p)2 (π2p)2
d. (σ2s)2 (σ2s)2 (σ2p)2 (π2p)2 (π2p)2 (π2p)1 (π*2p)1
e. (σ2s)2 (σ2s)2 (σ2p)2 (σ2p)2 (π2p)1 (π2p)1 (π2p)1 (π2p)1
d. (σ2s)2 (σ2s)2 (σ2p)2 (π2p)2 (π2p)2 (π2p)1 (π*2p)1
Who proposed the kinetic theory of gas?
a. Bernoulli
b. Einstein
c. Newton
d. Maxwell
a. Bernoulli
Vapors undergo a deposition process to convert into a solid. What is the change in density after this change of state?
a. It increases.
b. It decreases.
c. It remains the same.
d. It becomes zero.
a. It increases.
Case:
Metastable technetium-99m (99mTc) is the most medically important radionuclide, used for nearly 20 million diagnostic imaging procedures every year. The short 6-hour half-life of technetium-99m requires it to be transported to medical sites as its parent nuclide molybdenum-99 (99Mo, atomic number 42) in devices known as technetium-99m generators, which provide shielding to absorb the radiation released during the spontaneous decay of 99Mo to form 99mTc.
Question:
What best describes the nuclear decay process that occurs in technetium-99m generators and what is the atomic number of the decay product formed? (Note: the anti-matter produced or consumed during the following radioactive decay processes is not shown.)
a. Beta minus decay 99 Mo→ 99 mTc + β−
Atomic number: Z=43
b. Alpha decay 99 Mo→ 99 mTc + α
Atomic number: Z=40
c. Positron emission 99 Mo→ 99 mTc + β+
Atomic number: Z=41
d. Electron capture 99 Mo + β− → 99 mTc
Atomic number: Z=41
e. Gamma decay 99 Mo→ 99 mTc + γ
Atomic number: Z=42
a. Beta minus decay 99 Mo→ 99 mTc + β−
Atomic number: Z=43
Which of the following is true according to the ideal gas law?
a. The absolute pressure of a gas is directly proportional to its volume.
b. The volume of a gas is inversely proportional to its temperature.
c. The absolute pressure of a gas is directly proportional to its temperature.
d. The volume of a gas is inversely proportional to its number of moles.
c. The absolute pressure of a gas is directly proportional to its temperature.
According to the pH scale, what does pH 7 indicate for a solution?
a. Neutral
b. Basic
c. Acidic
d. Acidic and basic
a. Neutral
Which of the following bonds has the least covalent character? Refer to the image.
a. AlCl3
b. CaO
c. NaBr
d. AsCl
b. CaO
Which contains 2 resonance structures? Refer to the image.
a. A
b. B
c. C
d. D
c. C
Case:
An electrochemical cell is built in the classroom using a KOH salt bridge and similar electrode materials to those used in consumer-grade alkaline batteries. The cell is constructed to provide conditions favorable to the same half-reactions observed in the dry cell batteries. A schematic of the cell is shown below. Refer to the image.
Question:
Alkaline batteries are galvanic (voltaic) cells that power an external load connected by conductive material to the anode and the cathode. Electrons spontaneously released at the anode travel through the conductor, across the load, and then reduce ions at the surface of the cathode. The path traveled by the electrons comprises one-half of a closed-circuit present in the cell.
What is the other half of the closed circuit and its function in galvanic/voltaic cells?
a. Galvanic/voltaic cells form a closed circuit when they are connected to an external load with a potential equivalent to that of the galvanic cell (after over-potentials are considered).
b. The salt bridge provides an alternative path for the flow of a counter current of electrons between the electrodes to provide charge balancing for the spontaneous flow of electrons of the anode to the cathode.
c. If the electrodes and electrolytes in each half-cell are chosen correctly, the half-reactions occurring at the anode and cathode are balanced and will proceed spontaneously to completion by simply grounding the cell in order to close the circuit.
d. Ions in the electrolyte solutions and the salt bridge carry electrical charge and maintain electrical neutrality by migrating between the half-cells to counter the charge carried by electrons flowing from the anode to the cathode.
e. Placing the electrodes into separate cells containing electrolytes with cations that can be reduced at the cathode allows the electrochemical reaction to spontaneously proceed forward.
d. Ions in the electrolyte solutions and the salt bridge carry electrical charge and maintain electrical neutrality by migrating between the half-cells to counter the charge carried by electrons flowing from the anode to the cathode.
Given the reduction potential of various metals, write a balanced redox equation for the spontaneous generation of hydrogen gas from a basic solution by one of the following metals: Na, Cr, Cd, Pt, Al.
a. Na(s) + 2H2O(l) → Na+(aq) + H2(g) + 2OH-(aq)
b. 2Cr(s) + 6H2O(l) → 2Cr3+(aq) + 3H2(g) + 6OH-(aq)
c. Cd(s) + 2H2O(l) → Cd2+(aq) + H2(g) + 2OH-(aq)
d. Pt(s) + 2H2O(l) → Pt2+(aq) + H2(g) + 2OH-(aq)
e. 2Al(s) + 6H2O(l) → 2Al3+(aq) + 3H2(g) + 6OH-(aq)
e. 2Al(s) + 6H2O(l) → 2Al3+(aq) + 3H2(g) + 6OH-(aq)
How many oxygen atoms are in 10.5 g of sodium perxenate, Na4XeO6?
a. 7.9 x 1022 atoms O
b. 1.98 x 1022 atoms O
c. 0.0329 atoms O
d. 1.19 x 1023 atoms O
e. 1.2 x 1022 atoms O
b. 1.98 x 1022 atoms O
The first step to determine the number of molecules from the mass of a sample is to convert the mass to moles by dividing the mass by the molecular weight of the compound: 10.5 g/319.21 g/mol = 0.0329 mol. Then multiply the number of moles by Avogadro’s number: 0.0329 mol * 6.022 x 1023 molecules/mol = 1.98 x 1022 molecules. This value is the number of molecules of sodium perxenate, which contains 6 atoms of oxygen, so multiply by 6 to get atoms of oxygen: 1.98 x 1022 * 6 = 1.19 x 1023 atoms O.
What charge can be calculated for a chlorine atom containing 18 electrons?
a. -2
b. -1
c. +1
d. +2
b. -1
Which of the following is a correct and balanced equation of a reaction between aluminum and sulfur?
a. Al + S8 →AlS8
b. 4Al + S8 → 4AlS2
c. 12Al + S8 → 4Al3S2
d. 16Al + 3S8 → 8Al2S3
d. 16Al + 3S8 → 8Al2S3
Case:
The octet rule dictates that atoms of the main-group elements tend to form bonds in such a way that leads to each atom having 8 electrons in its valence shell, but there are exceptions to this rule.
Question:
What makes up the valence shell of iodine in the compound ICl4-?
a. 4 shared pairs of valence electrons in σ-bonds with the chlorine atoms, a lone pair in a d-orbital, and an unpaired electron in a d-orbital
b. 4 shared pairs of valence electrons in σ-bonds with the chlorine atoms and 2 lone pairs in d-orbitals
c. 8 valence electrons with 4 pairs of valence electrons in σ-bonds
d. Octet with 4 electrons in σ-bonds and a lone pair in a p-orbital
b. 4 shared pairs of valence electrons in σ-bonds with the chlorine atoms and 2 lone pairs in d-orbitals
