1.
Which of the following is the essential characteristic of a polar molecule?
Correct Answer
D. Has an asymmetrical distribution of electrical charge
Explanation
A polar molecule is one in which there is an uneven distribution of electrical charge. This means that one end of the molecule has a slight positive charge, while the other end has a slight negative charge. This occurs when the electrons in the molecule are not evenly shared between the atoms, resulting in an asymmetrical distribution of charge. The other options, such as containing double or triple bonds, being formed at extremely low temperatures, containing ions, or containing the element oxygen, do not necessarily indicate a polar molecule.
2.
One of the ways organisms maintain a stable internal environment (homeostasis) is to use buffers to keep the pH of their body fluids within narrow limits. A biology student mixes 200 mL of a buffered solution with a pH of 4 (solution 'X') with 200 mL of a base (solution 'Y'). After mixing, the pH of the resulting solution (solution 'Z') was found to have risen to 5. Which of the following statements can be made in connection with the experiment described?1. Solution 'Z' contains more hydroxyl ions per unit volume than solution 'Y'2. There were 10 times as many hydronium ions in solution 'X' per unit volume than there were in solution 'Z'3. Solution 'Z' contains a higher concentration of hydronium ions than solution 'X'4. Solution 'Y' used up all of the buffering action of solution 'X'5. The pH of solution 'B' was 8
Correct Answer
D. 2 and 4
Explanation
The pH of the resulting solution (solution 'Z') increased from 4 to 5, indicating that it became less acidic. This suggests that solution 'Y' was a base and neutralized some of the hydronium ions (H+) present in solution 'X'. Therefore, statement 2 is correct, as there were fewer hydronium ions in solution 'Z' compared to solution 'X'. Additionally, statement 4 is correct because the buffering action of solution 'X' was used up by the base in solution 'Y', resulting in the increase in pH.
3.
Which three of the following are characteristics of hydrogen bonds?1. They are responsible for the surface tension properties of water.2. They are responsible for the relatively high boiling point of water.3. They are strong than ionic bonds.4. They are present in all substances.5. They are weaker than covalent bonds.
Correct Answer
A. 1, 2, and 5
Explanation
Hydrogen bonds are responsible for the surface tension properties of water because they create a cohesive force between water molecules, causing them to stick together. They are also responsible for the relatively high boiling point of water because the hydrogen bonds need to be broken in order for the water molecules to change from a liquid to a gas state. Lastly, hydrogen bonds are weaker than covalent bonds because they involve the attraction between a hydrogen atom and an electronegative atom, such as oxygen or nitrogen, rather than a sharing of electrons between atoms.
4.
When atoms from two different elements are brought together under conditions that will favour a reaction and the have similar electronegativities, which type of chemical bond is most likely to form?
Correct Answer
C. Nonpolar covalent bond
Explanation
When atoms from two different elements have similar electronegativities, it means that they have similar abilities to attract electrons. In this case, they are likely to form a nonpolar covalent bond. In a nonpolar covalent bond, the electrons are shared equally between the atoms, resulting in a balanced distribution of charge. This type of bond occurs when the electronegativity difference between the atoms is very small or nonexistent.
5.
A chemical bond involving carbon and hydrogen (C-H) is present in many biological molecules. Based upon their electronegativities, the bond could be described as:
Correct Answer
B. A covalent bond
Explanation
The correct answer is a covalent bond. A covalent bond is formed when two atoms share electrons. In the case of a C-H bond, carbon and hydrogen share electrons to form a stable molecule. This type of bond is common in organic compounds and is characterized by the equal sharing of electrons between the carbon and hydrogen atoms. It is not an ionic bond because there is no transfer of electrons, and it is not a hydrogen bond because hydrogen bonds occur between a hydrogen atom and an electronegative atom such as oxygen or nitrogen.
6.
In looking at the periodic table, the following information would be found about nitrogen:147NFrom the above, it can be determined that an atom of nitrogen has the following characteristics:
Correct Answer
E. It has an atomic mass of 14 atomic mass units and 7 electrons
Explanation
The answer is correct because it accurately describes the characteristics of an atom of nitrogen. The atomic mass of nitrogen is 14 atomic mass units, which is the sum of its protons and neutrons. Additionally, nitrogen has 7 electrons, which is equal to its number of protons. Therefore, the answer correctly states that nitrogen has an atomic mass of 14 atomic mass units and 7 electrons.
7.
Element 'X' has 7 electrons in the outermost energy level of each of its atoms. Atoms of element 'Y' also contain 7 electrons in the outermost energy level. However, when neutral, element 'Y' has a much lower atomic mass. Therefore:
Correct Answer
C. Both elements will form covalent bonds more readily than ionic bonds
Explanation
Element 'X' has a lower electronegativity than element 'Y'
Both elements will tend to give up an electron to become chemically stable
Both elements will form covalent bonds more readily than ionic bonds
It is highly probable that these elements will form polar covalent molecules
There is not enough information to answer this question
8.
Isomers are molecules that:
Correct Answer
A. Have the same molecular formula
Explanation
Isomers are molecules that have the same molecular formula, meaning they have the same number and types of atoms. However, they differ in their arrangement of atoms, resulting in different structural or spatial arrangements. This can lead to differences in their physical and chemical properties. Therefore, isomers have the same molecular formula but different structures.
9.
In living organisms, buffers do which of the following?
Correct Answer
E. Maintain pH in the cells within a narrow range, allowing enzymes to function
Explanation
Buffers in living organisms help maintain the pH within a narrow range, which is crucial for the proper functioning of enzymes. Enzymes are highly sensitive to changes in pH, and even slight deviations from their optimal pH can disrupt their structure and function. By regulating the pH, buffers ensure that enzymes can maintain their active conformation and catalyze biochemical reactions efficiently. This is essential for various cellular processes and overall organismal homeostasis.
10.
By what factor would the concentration of hydrogen (hydronium) ions be decreased if the pH of a solution changed from 4.5 to 6.5?
Correct Answer
D. 100
Explanation
The pH of a solution is a measure of the concentration of hydrogen ions (H+) in the solution. A decrease in pH indicates an increase in the concentration of H+ ions, while an increase in pH indicates a decrease in the concentration of H+ ions. In this case, the pH is changing from 4.5 to 6.5, which means it is increasing by 2 units. Since pH is a logarithmic scale, a change of 2 units represents a 100-fold decrease in the concentration of H+ ions. Therefore, the concentration of H+ ions would be decreased by a factor of 100.
11.
How many electrons are involved in each covalent bond?
Correct Answer
A. 2
Explanation
In a covalent bond, two atoms share a pair of electrons. Each atom contributes one electron to the bond, resulting in a total of two electrons involved in the bond. Therefore, the correct answer is 2.
12.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.What makes water a highly polar molecule? ______Terms:1. London dispersion2. Polar covalent bonds and symmetrical structure3. Intermolecular4. Hydrophobic5. Van der Waals forces6. Hydrogen bond7. Polar covalent bonds and asymmetrical structure8. Intramolecular9. Hydrophilic10. Dipole-dipole
Correct Answer
7
Explanation
Water is a highly polar molecule because it has polar covalent bonds and an asymmetrical structure. The oxygen atom in water is more electronegative than the hydrogen atoms, causing the oxygen to have a partial negative charge and the hydrogen atoms to have partial positive charges. This uneven distribution of charge creates a dipole moment, making water a polar molecule.
13.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What are bonds between molecules called? ______
Terms:
1. London dispersion
2. Polar covalent bonds and symmetrical structure
3. Intermolecular
4. Hydrophobic
5. Van der Waals forces
6. Hydrogen bond
7. Polar covalent bonds and asymmetrical structure
8. Intramolecular
9. Hydrophilic
10. Dipole-dipole
Correct Answer
3
Explanation
The term "intermolecular" refers to the bonds between molecules.
14.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What is the only force of attraction between noble gases? ______
Terms:
1. London dispersion
2. Polar covalent bonds and symmetrical structure
3. Intermolecular
4. Hydrophobic
5. Van der Waals forces
6. Hydrogen bond
7. Polar covalent bonds and asymmetrical structure
8. Intramolecular
9. Hydrophilic
10. Dipole-dipole
Correct Answer
1
Explanation
The only force of attraction between noble gases is London dispersion.
15.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What force is responsible for holding polar molecules to one another? ______
Terms:
1. London dispersion
2. Polar covalent bonds and symmetrical structure
3. Intermolecular
4. Hydrophobic
5. Van der Waals forces
6. Hydrogen bond
7. Polar covalent bonds and asymmetrical structure
8. Intramolecular
9. Hydrophilic
10. Dipole-dipole
Correct Answer
10
Explanation
The force responsible for holding polar molecules to one another is dipole-dipole interactions. This occurs when the positive end of one polar molecule attracts the negative end of another polar molecule, creating a bond between them. This force is stronger than the London dispersion forces, which are present in all molecules, and weaker than hydrogen bonding, which occurs when a hydrogen atom is bonded to a highly electronegative atom like oxygen or nitrogen.
16.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What dipole-dipole force results between H and either N, O or F? ______
Terms:
1. London dispersion
2. Polar covalent bonds and symmetrical structure
3. Intermolecular
4. Hydrophobic
5. Van der Waals forces
6. Hydrogen bond
7. Polar covalent bonds and asymmetrical structure
8. Intramolecular
9. Hydrophilic
10. Dipole-dipole
Correct Answer
6
Explanation
A hydrogen bond is a type of dipole-dipole force that occurs between a hydrogen atom bonded to a highly electronegative atom (such as N, O, or F) and another electronegative atom. This bond is stronger than other dipole-dipole forces because of the large electronegativity difference between hydrogen and the other atom. Therefore, the correct answer is 6.
17.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What is the collective name for intermolecular bonding? ______
Terms:
1. London dispersion
2. Polar covalent bonds and symmetrical structure
3. Intermolecular
4. Hydrophobic
5. Van der Waals forces
6. Hydrogen bond
7. Polar covalent bonds and asymmetrical structure
8. Intramolecular
9. Hydrophilic
10. Dipole-dipole
Correct Answer
5
Explanation
The correct answer is "Van der Waals forces." Van der Waals forces refer to the collective name for intermolecular bonding, which includes London dispersion, dipole-dipole interactions, and hydrogen bonding. These forces are responsible for the attractions between molecules and determine many of their physical properties.
18.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What is a property of nonpolar molecules? ______
Terms:
1. London dispersion
2. Polar covalent bonds and symmetrical structure
3. Intermolecular
4. Hydrophobic
5. Van der Waals forces
6. Hydrogen bond
7. Polar covalent bonds and asymmetrical structure
8. Intramolecular
9. Hydrophilic
10. Dipole-dipole
Correct Answer
4
Explanation
A property of nonpolar molecules is that they are hydrophobic, meaning they do not dissolve in water.
19.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What is a property of polar molecules? ______
Terms:
1. London dispersion
2. Polar covalent bonds and symmetrical structure
3. Intermolecular
4. Hydrophobic
5. Van der Waals forces
6. Hydrogen bond
7. Polar covalent bonds and asymmetrical structure
8. Intramolecular
9. Hydrophilic
10. Dipole-dipole
Correct Answer
9
20.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What particle of an atom carries a positive charge? ______
Terms:
1. Isomer2. Electron3. Nucleus4. Tracers5. Neutron6. Isotopes7. Proton8. Half-life9. Radioisotopes10. Positron
Correct Answer
7
Explanation
A proton is a subatomic particle that carries a positive charge. It is located in the nucleus of an atom along with neutrons.
21.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What particle of an atom carries a negative charge? ______
Terms:
1. Isomer
2. Electron
3. Nucleus
4. Tracers
5. Neutron
6. Isotopes
7. Proton
8. Half-life
9. Radioisotopes
10. Positron
Correct Answer
2
Explanation
The particle of an atom that carries a negative charge is the electron.
22.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What particle of an atom carries a neutral charge? ______
Terms:
1. Isomer
2. Electron
3. Nucleus
4. Tracers
5. Neutron
6. Isotopes
7. Proton
8. Half-life
9. Radioisotopes
10. Positron
Correct Answer
5
Explanation
The particle of an atom that carries a neutral charge is the neutron.
23.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What are atoms of the same element with different mass numbers called? ______
Terms:
1. Isomer
2. Electron
3. Nucleus
4. Tracers
5. Neutron
6. Isotopes
7. Proton
8. Half-life
9. Radioisotopes
10. Positron
Correct Answer
6
Explanation
Atoms of the same element with different mass numbers are called isotopes.
24.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What kind of atoms spontaneously decay? ______
Terms:
1. Isomer
2. Electron
3. Nucleus
4. Tracers
5. Neutron
6. Isotopes
7. Proton
8. Half-life
9. Radioisotopes
10. Positron
Correct Answer
9
Explanation
Radioisotopes spontaneously decay.
25.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What is the time for half of the atoms in a sample to decay called? ______
Terms:
1. Isomer
2. Electron
3. Nucleus
4. Tracers
5. Neutron
6. Isotopes
7. Proton
8. Half-life
9. Radioisotopes
10. Positron
Correct Answer
8
Explanation
The time for half of the atoms in a sample to decay is called the half-life.
26.
Match an item in the list of terms to the statement below. Enter your numbered choice in the text box.
What is a useful application of unstable atoms? ______
Terms:
1. Isomer
2. Electron
3. Nucleus
4. Tracers
5. Neutron
6. Isotopes
7. Proton
8. Half-life
9. Radioisotopes
10. Positron
Correct Answer
4
Explanation
Tracers are a useful application of unstable atoms. Tracers are substances that are used to track the movement or progress of a process. Unstable atoms, or radioisotopes, can be used as tracers because their radioactive decay can be easily detected and measured. This allows scientists to monitor the movement of these atoms in various systems, such as in medical imaging or environmental studies.