June 2023
10 What is the number of electrons shared between the two atoms in an O2 molecule? (1) 6
(2) 2 (3) 3
(4) 4
Solution: Oxygen can be found on the Periodic Table. Its electron configuration is 2-6 which means it has 6 valence electrons. Each element (other than H and He) wants 8 valence elections. It needs 2 more electrons to have 8. Therefore, when an oxygen atom will bond to another oxygen atom, it will form a double bond. Each bond has 2 electrons. Double bond has 2*2= 4 electrons
Answer: 4
17 Which statement explains the low boiling point of hydrogen, H2, at standard pressure? (1) Hydrogen has strong covalent bonds. (2) Hydrogen has weak covalent bonds. (3) Hydrogen has strong intermolecular forces.
(4) Hydrogen has weak intermolecular forces.
Solution: The stronger the intermolecular forces, the higher the boiling point of a substance. Since, H2 has a low boiling point, it must have weak intermolecular forces.
Answer: 4
39 Based on Table H, which compound has the strongest intermolecular forces at 60 kPa?
(1) ethanoic acid
(2) ethanol (3) propanone
(4) water
Solution: The stronger the intermolecular forces, the lower the vapor pressure of a compound. We need to look at Table H and find 60kPa on the x-axis and then go up until we touch the line for each compound listed to see its vapor pressure. The ones with the lowest vapor pressure will have the strongest intermolecular forces.
Answer:1
January 2023
Which type of bond forms when electrons are equally shared between two atoms?
(1) a polar covalent bond
(2) a nonpolar covalent bond
(3) a hydrogen bond
(4) an ionic bond
Solution: A nonpolar covalent bond is a bond where electrons are equally shared. In a polar covalent bond, electrons are shared unequally. In an ionic bond, electrons are transferred. A hydrogen bond is an intermolecular force between molecules containing OH, NH or FH.
Answer:2
12 The degree of polarity in the bond between a hydrogen atom and an oxygen atom in a molecule of water can be assessed using the difference in
(1) densities
(2) electronegativities
(3) melting points
(4) intermolecular forces
Solution: The degree of polarity of a bond is assessed by calculating the electronegativity difference between the two atoms that share the bond.
Answer: Choice 2 is the correct answer choice.
41 What is the vapor pressure of propanone at 45°C? (1) 21 kPa
(2) 60. kPa
(3) 70. kPa
(4) 79 kPa
Solution:We need to look at Table H and find 45°C on the x-axis and then go up until we touch the line for propanone. Then we go to the right to find the vapor pressure of the y axis.
Answer: 3
August 2022
11. Which terms represent two categories of compounds?
(1) chemical and physical
(2) chemical and molecular
(3) ionic and physical
(4) ionic and molecular
Solution: Two categories of compounds are ionic and molecular. Ionic compounds consist of a metal with a nonmetal (such as NaCl) or a metal with a polyatomic ion (such as LiOH). Covalent compounds consist of two or more nonmetals bonded together (such as CH4).
Answer: 4
37 An atom of which element bonds with an atom of hydrogen to form the most polar bond?
(1) bromine
(2) chlorine
(3) fluorine
(4) iodine
Solution: The most polar bond results from the biggest electronegativity difference. For this question, let's take a look at the Table S on the reference table which lists all the elements and their electronegativity values. Bromine =3.0 Chlorine=3.2 Fluorine = 4.0 Iodine=2.7 Hydrogen = 2.2
Next for each combination of elements we subtract smallest number form the biggest to get the electronegativity difference. For example, HF = 4.0-2.2 = 1.8 Whoever has the largest electronegativity difference, has the most polar bond. HF should be most polar. Alternatively, we might know that fluorine is the most electronegative element on the periodic table and will result in the most polar bond with hydrogen.
Answer: 3
June 2022
7 How many electrons are shared in a triple bond between two atoms?
(1) 6
(2) 2
(3) 3
(4) 4
Solution: Each covalent bond is form from the sharing of 2 electrons. A triple bond has three bonds in it. Therefore, 3*2=6
Answer: 1
35 A substance conducts electricity in the liquid phase but not in the solid phase. This substance can be classified as
(1) covalent
(2) ionic
(3) metallic
(4) molecular
Solution: Substances that conduct electricity in liquid but not in the solid phase are ionic. Metallic substances conduct electricity in all phases. Covalent/molecular substances do not conduct electricity.
Answer: 2
37 Which chemical bond is most polar?
(1) a O–H bond in H2O
(2) a S–H bond in H2S
(3) a Se–H bond in H2Se
(4) a Te–H bond in H2Te
Solution: The polarity of the bond is based on the electronegativity difference. Electronegativity values can be found in Table S on the Reference Table. All we need to do is to find electronegativity value for each element holding a bond. Then, subtract the bigger number from the smaller number to find electronegativity difference. The pair that has the largest electronegativity difference represents the most polar bond.
Answer: 1
January 2020
7 Which terms identify two different categories of compounds? (1) covalent and molecular
(2) covalent and empirical
(3) ionic and molecular (4) ionic and empirical
Solution: Ionic and molecular are two different categories of compounds. Empirical formula is a formula with simplest ratio of atoms and is not a category of a compound. Covalent is a type of bond that is found in molecular compounds.
Answer: 3
14 Which term identifies a type of intermolecular force? (1) covalent bonding
(2) hydrogen bonding (3) ionic bonding
(4) metallic bonding
Solution: Hydrogen bonding, dipole-dipole, and dispersion forces are all types of intermolecular forces.
Answer: 2
40 The bond between which two atoms is most polar? (1) C–O
(2) F–F (3) H–O
(4) N–H
Solution:The polarity of the bond is based on the electronegativity difference. Electronegativity values can be found in Table S on the Reference Table. All we need to do is to find electronegativity value for each element holding a bond. Then, subtract the bigger number from the smaller number to find electronegativity difference. The pair that has the largest electronegativity difference represents the most polar bond.
Answer: 3
August 2019
11 Which element has metallic bonds at room temperature? (1) bromine
(2) cesium
(3) krypton
(4) sulfur
Solution: Metals have metallic bonds. Metals are to the left of the staircase on the Periodic Table.
Answer: 2
12 What is the number of electrons shared between the atoms in a molecule of nitrogen, N2? (1) 8
(2) 2
(3) 3
(4) 6
Solution: Nitrogen can be found on the Periodic Table. Its electron configuration is 2-5 which means it has 5 valence electrons. Each element (other than H and He) wants eight valence elections. Nitrogen needs three more electrons to have eight. Therefore, a nitrogen atom will bond with another nitrogen atom via a triple bond. Each bond has 2 electrons. Triple bond has 2*3= 6 electrons
Answer: 4
36 Which compound has covalent bonds? (1) H2O
(2) Li2O
(3) Na2O
(4) K2O
Solution: Covalent bonds are formed between two nonmetals. Nonmetals can be found on the right side of the staircase on the Periodic Table. Hydrogen is a nonmetal as well.
Li, Na, and K are all metals and will form ionic bonds with oxygen.
Answer: 1
June 2019
12 The degree of polarity of a covalent bond between two atoms is determined by calculating the difference in their
(1) atomic radii
(2) melting points
(3) electronegativities
(4) ionization energies
Solution: The difference in electronegativity determines how polar a covalent bond is. The higher the difference, the more polar the bond.
Answer: Choice 3
39 The molar masses and boiling points at standard pressure for four compounds are given in the table below.
Which compound has the strongest intermolecular forces?
(1)HF
(2)HCl
(3)HBr
(4)HI
Solution: The higher the boiling point, the stronger the intermolecular forces.
Answer: Choice 1
January 2019
9 Which two terms represent types of chemical formulas? (1) empirical and molecular (2) polar and nonpolar (3) synthesis and decomposition
(4) saturated and concentrated
Solution: Let's look at the answer choices to find the two terms represent types of chemical formulas. Polar and nonpolar refer to types of bonds or types of molecules. Synthesis and decomposition are two kinds of reactions. Saturated and concentration refer to solutions. Empirical is a formula with smallest whole number ratios of atoms. Molecular formula is a formula that shows the number of atoms of each element present in a molecule.
Answer:1
August 2018
10 Which two terms represent major categories of compounds? (1) ionic and nuclear (2) ionic and molecular (3) empirical and nuclear
(4) empirical and molecular
Solution: ionic and molecular are two terms that represent major categories of compounds.
Answer: 2
13 A solid sample of copper is an excellent conductor of electric current. Which type of chemical bonds are in the sample? (1) ionic bonds (2) metallic bonds (3) nonpolar covalent bonds
(4) polar covalent bonds
Solution: Copper is a metal because it can be found on the left side of the staircase on the Periodic Table. Metals have metallic bonds.
Answer: 2
19 Compared to H2S, the higher boiling point of H2O is due to the (1) greater molecular size of water (2) stronger hydrogen bonding in water
(3) higher molarity of water (4) larger gram-formula mass of water
Solution: Compounds with stronger intermolecular forces have higher boiling points. Hydrogen bonding is a type an intermolecular force and is present between molecules that have OH, NH or HF which H2O but not H2S has.
Answer:2
39 The least polar bond is found in a molecule of
(1) HI (2) HF
(3) HCl
(4) HBr
Solution: The polarity of the bond is based on the electronegativity difference. Electronegativity values can be found in Table S on the Reference Table. All we need to do is to find electronegativity value for each element holding a bond. Then, subtract the bigger number from the smaller number to find electronegativity difference. The pair that has the smallest electronegativity difference represents the least polar bond.
Answer:1
January 2018
9 Which phrase describes the molecular polarity and distribution of charge in a molecule of carbon dioxide, CO2? (1) polar and symmetrical (2) polar and asymmetrical (3) nonpolar and symmetrical
(4) nonpolar and asymmetrical
Solution: CO2 has the following structural formula: O=C=O. It is a symmetrical molecule and is therefore nonpolar. Symmetrical molecules are nonpolar and asymmetrical molecules are polar.
Answer: 3
37 Which bond is most polar? (1) C–O
(2) H–O
(3) N–O
(4) S–O
Solution:The polarity of the bond is based on the electronegativity difference. Electronegativity values can be found in Table S on the Reference Table. All we need to do is to find electronegativity value for each element holding a bond. Then, subtract the bigger number from the smaller number to find electronegativity difference. The pair that has the highest electronegativity difference represents the most polar bond.
Answer: 2
42 Based on Table H, what is the vapor pressure of CH3COOH at 90.°C? (1) 40. kPa
(2) 48 kPa
(3) 114 kPa
(4) 150. kPa
Solution: We need to look at Table H and find 90°C on the x-axis and then go to the up until we touch the line for ethanoic acid. Then we go to the left to find the vapor pressure of the y axis.
Answer:1
June 2017
12 Which substance has nonpolar covalent bonds? (1) Cl2
(2) SO3
(3) SiO2
(4) CCl4
Solution: A bond between two atoms of the same element is nonpolar covalent.
Answer: 1
13 What is the vapor pressure of propanone at 50.°C?
(1) 37 kPa
(2) 50. kPa (3) 83 kPa
(4) 101 kPa
Solution: We need to look at Table H and find 50°C on the x-axis and then go to the up until we touch the line for propanone. Then we go to the left to find the vapor pressure of the y axis.
Answer:1
37 The particle diagram below represents a solid sample of silver.
Which type of bonding is present when valence electrons move within the sample?
(1) metallic bonding
(2) hydrogen bonding (3) covalent bonding
(4) ionic bonding
Solution: Silver is a metal because it can be found on the left side of the staircase on the Periodic Table. Metals have metallic bonds.
Answer:1
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