Title: Chemistry of Life
Course: Question Banks

Q: Pick the most complete answer. All living organisms contain ________.
- carbon
- carbon and oxygen
- carbon, oxygen, hydrogen, and nitrogen.
A: carbon, oxygen, hydrogen, and nitrogen.

Q: The most common element in humans is ________.
- carbon (Incorrect. Even though we are carbon-based lifeforms, carbon is not the most common element in humans.)
- nitrogen (Incorrect. Nitrogen is the least common element in humans.)
- oxygen (Correct. Oxygen is the most common element in humans, making up 65 percent of a person.)
A: oxygen

Q: Which of the following is the fundamental unit of matter?
- The electron (Incorrect. An electron is a subparticle of the fundamental unit of matter.)
- The cell (Incorrect. A cell is the fundamental unit of life, not of matter.)
- The atom (Correct. The atom is the most basic unit of matter.)
A: The atom

Q: An atom’s________ are disregarded when calculating its mass.
- neutrons (Incorrect. Neutrons provide a vital contribution to the mass of an atom.)
- protons (Incorrect. Protons provide a vital contribution to the mass of an atom.)
- electrons (Correct. Electrons provide an insignificant amount of the mass of an atom and therefore are disregarded when calculating atomic mass.)
A: electrons

Q: Using the accompanying figure to answer the following question. Which letter indicates the neutrons of the atom?
- A (Incorrect. These particles are electrons.)
- C (Incorrect. These particles are protons.)
- D (Incorrect. B and C together make up the nucleus of an atom.)
- B (Correct. These particles are neutrons.)
A: B

Q: Atoms are composed of a ________.
- membrane (Incorrect. Atoms do not have membranes.)
- force field (Incorrect. Atoms do not have a force field.)
- nucleus (Correct. This is one component of an atom.)
A: nucleus

Q: The number and arrangement of ________ controls how elements interact.
- protons (Incorrect. The number of protons determines an element’s atomic number and contributes to its mass number.)
- neutrons (Incorrect. The number of neutrons contributes to an element’s mass number.)
- electrons (Correct. The number of electrons indicates how many energy shells around an element are filled. This arrangement in turn controls how elements interact.)
A: electrons

Q: The ________ of electrons controls how elements interact.
- size (Incorrect. Electrons are always the same size.)
- size and arrangement (Incorrect. Electrons are always the same size.)
- number and arrangement (Correct. The number of electrons indicates how many energy shells around an element are filled. This arrangement in turn controls how elements interact.)
A: number and arrangement

Q: Which element has only two electrons?
- carbon (Incorrect. Carbon has more than one electron shell and therefore more than two electrons.)
- hydrogen (Incorrect. Hydrogen has only one electron shell, but it is not full.)
- helium (Correct. Helium has a full first shell, which holds two electrons.)
A: helium

Q: Carbon-12 and Carbon-13 are two forms of the same element, carbon. They have the same number of protons, but different numbers of neutrons. Atoms of an element that have a different number of neutrons are called ________
- anions (Incorrect. Anions are a negatively charged ions)
- positrons (Incorrect. A positron is a subatomic particle with the same mass as an electron and a numerically equal but positive charge)
- isotopes (Correct: Isotopes are different forms of the same element that contain equal numbers of protons but not the same number of neutrons)
A: isotopes

Q: Look at this image:

How are these three elements different from each other?
- They are combinations of the element hydrogen. (Incorrect. These are not combinations of hydrogen.)
- Protium and Deuterium combine to form Tritium. (Incorrect: These are different forms of hydrogen.)
- They are all isotopes of the element hydrogen. (Correct. Protium, Deuterium and Tritium are different forms of hydrogen.)
A: They are all isotopes of the element hydrogen.

Q: According to the ________, atoms want their outer electron shells to be filled.
- valence shell (Incorrect. The valence shell is simply the name of the outermost electron shell.)
- orbital rule (Incorrect. An orbital is the path an electron follows around an atom’s nucleus.)
- octet rule (Correct. The octet rule states that atoms are energetically more stable with their outer shell filled with electrons.)
A: octet rule

Q: Neon (Atomic number 10) has more than one electron shell and the outermost shell contains eight electrons. What is the outcome of such electron configuration?
- It forms covalent bonds in an aqueous solution. (Incorrect. The chemical behavior of an atom is determined by the number of electrons in its outermost shell. If it is incomplete, it will carry out chemical reactions. On the other hand, neon gas, in which the outermost shell is complete is chemically unreactive.)
- It becomes extremely unstable and reactive. (Incorrect. The chemical behavior of an atom is determined by the number of electrons in its outermost shell. If it is incomplete, it will carry out chemical reactions. On the other hand, neon gas, in which the outermost shell is complete is chemically unreactive.)
- It is stable and inert (Correct. The chemical behavior of an atom is determined by the number of electrons in its outermost shell. If it is incomplete, it will carry out chemical reactions. On the other hand, neon gas, in which the outermost shell is complete is chemically unreactive.)
A: It is stable and inert

Q: Look at the image below.

Based on the distribution of electrons, which would you expect to be least likely to form a chemical bond with another atom?
- Na (Incorrect. The valence shell of Sodium is incomplete. Therefore, it will be reactive.)
- Mg (Incorrect. The valence shell of Magnesium is incomplete. Therefore, it will be reactive.)
- Si (Incorrect. The valence shell of Silicon is incomplete. Therefore, it will be reactive.)
- Ar (Correct. The valence shell of Argon is complete. Therefore, it will be unreactive.)
A: Ar

Q: In an ionic bond, the charge on the cation is ________.
- always negative (Incorrect. Cations are not always negative.)
- either negative or positive (Incorrect. Cations are characterized by a single charge.)
- always positive (Correct. Cations are always positive.)
A: always positive

Q: Which of the following best explains the natural formation of ions?
- a filled outer electron shell and a large electronegativity differential (Incorrect. This describes a hydrogen bond, which you have yet to cover.)
- an unfilled outer electron shell and electron sharing (Incorrect. This describes the formation of a covalent bond, which you have yet to cover.)
- an unfilled outer electron shell and electron transfer (Correct. It is the transfer of electrons that creates the positive and negative charges associated with ions.)
A: an unfilled outer electron shell and electron transfer

Q: Which of the following is a correct statement?
- Covalent bonds lead to molecules that are stable in air while ionic bonds do not. (Incorrect. No bond type is automatically more or less stable in air.)
- ​Covalent bonds only occur between atoms of similar electronegativities while ionic bonds only occur between atoms of differing electronegativities. (Incorrect. Electronegativities play a role in hydrogen bonds only.)
- Ionic bonds to do not share valence electrons while covalent bonds do. (Correct. Covalent bonds involve sharing of electrons.)
A: Ionic bonds to do not share valence electrons while covalent bonds do.

Q: Double bonds form when ________ of electrons are shared.
- one pair (Incorrect. Sharing one pair of electrons is a single bond.)
- three pairs (Incorrect. Sharing three pairs of electrons results in a triple bond.)
- two pairs (Correct. Sharing two pairs of electrons generates a double bond.)
A: two pairs

Q: Select the bond that is most polar.
- N ≡ N (Incorrect. Because this bond involves only N, the electrons will be shared equally.)
- O = C (Incorrect. This will be a polar bond but the size differential between C and O is not the largest in the answer choices.)
- O – H (Correct. Because O is much larger than H, it will attract electrons more strongly.)
A: O – H

Q: Which type of bond represents a weak chemical bond?
- covalent bond (Incorrect. Covalent bonds are the strongest type of bonds because they involve shared electrons.)
- ionic bond (Incorrect. Ionic bonds are not the strongest bonds, but they are quite strong.)
- hydrogen bond (Correct. Hydrogen bonds are weak chemical attractions based on differences in electronegativity.)
A: hydrogen bond

Q: Which type of bond enables many of the properties of water?
- polar covalent bond (Incorrect. Individual molecules of water are formed by polar covalent bonds between H and O but this is not what enables many of the properties of water.)
- nonpolar covalent bond (Incorrect. Individual molecules of water are formed by polar covalent bonds between H and O but this is not what enables many of the properties of water.)
- hydrogen bond (Correct. The weak hydrogen bonds between different molecules of water enable many of the properties of water.)
A: hydrogen bond

Q: When hydrogen is involved in a polar covalent bond, it has a ________.
- slight negative charge (Incorrect. Hydrogen is a small atom and is more likely to ‘lose’ its electron during a covalent sharing.)
- strong positive charge (Incorrect. Hydrogen only has a single electron so it cannot fully transfer it, which is required for a strong positive charge to form.)
- slight positive charge (Correct. Hydrogen is a small atom and is more likely to ‘lose’ its electron during a covalent sharing. This makes hydrogen slightly positive (less electronegative).)
A: slight positive charge

Q: What type of weak bond occurs when atoms and molecules are temporarily attracted to each other by virtue of their proximity and charge?
- a non-polar covalent bond (Incorrect. Non-polar covalent bonds tend to be strong chemical bonds.)
- an ionic bond (Incorrect. An ionic bond is a chemical bond where one atom gives its electrons to another.)
- a van der Waal interaction (Correct. The van der Waals force is the weak force of attraction between molecules that are close together.)
A: a van der Waal interaction

Q: Which of the following is an example of van der Waals force?
- an ionic bond (Incorrect. An ionic bond is a strong bond that occurs when there is a transfer of electrons between atoms.)
- a polar bond (Incorrect. A polar bond is a strong bond that occurs when atoms share electrons unequally.)
- a hydrogen bond (Correct. A hydrogen bond is the strongest type of van der Waals force.)
A: a hydrogen bond

Q: Which of the following is NOT a property of water?
- Water molecules have the tendency to stick together. (Incorrect. This is why water can move up from soil into branches and leaves of trees.)
- Water expands when it freezes (Incorrect. This is why ice floats.)
- Water dissolves hydrophobic substances easily. (Correct. Water dissolves hydrophilic substances easily.)
A: Water dissolves hydrophobic substances easily.

Q: Which of the following is a reason why water important for life?
- It is the major organic molecule for life. (Incorrect. Water is not an organic molecule.)
- It is found everywhere. (Incorrect. Water is found almost everywhere, but this is not why it is important for life.)
- It is a universal solvent. (Correct. Water can mix with a wide range of substances.)
A: It is a universal solvent.

Q: When acids are added to a solution, the pH should ________.
- increase (Incorrect. Acids do not cause pH to increase.)
- stay the same (Incorrect. Acids will change the pH.)
- decrease (Correct. Acids cause pH to decrease.)
A: decrease

Q: ________ are substances that release hydrogen ions.
- Basic substances (Incorrect. Basic solutions do not release hydrogen ions.)
- Neutral substances (Incorrect: Neutral solutions do not release hydrogen ions.)
- Acidic substances (Correct. The definition of an acid is a substance that releases hydrogen ions.)
A: Acidic substances

Q: Blood maintains a ________ pH.
- acidic (Incorrect. Blood is not acidic.)
- basic (Incorrect. Blood is not basic.)
- near-neutral (Correct. Blood is near-neutral to avoid damaging substances transported in it.)
A: near-neutral

Q: Using a pH meter, you find the pH of an unknown solution to be 8.0. How would you describe this solution?
- weakly acidic (Incorrect. A pH above 7 is not acidic.)
- strongly basic (Incorrect. Any pH near 7 is not “strong.”)
- weakly basic (Correct. This pH is above 7 but not by much, making it weakly basic.)
A: weakly basic

Q: Baking soda has a(n) ________ pH.
- acidic (Incorrect. Baking soda is not acidic.)
- near-neutral (Incorrect. Baking soda is not near-neutral.)
- basic (Correct. Baking soda is basic.)
A: basic

Q: ________ of hydrogen ions result in a high pH.
- Mid-range levels (Incorrect. Mid-range concentration of H^+ concentration would not provide high pH values.)
- High levels (Incorrect. The higher the H^+ concentration, the lower the pH value.)
- Low levels (Correct. The lower the H^+ concentration, the higher the pH value.)
A: Low levels

Q: Buffers function by ________.
- absorbing excess hydrogen and releasing hydroxide ions (Incorrect. This would result in a more basic solution.)
- releasing hydrogen and absorbing excess hydroxide ions (Incorrect. This would result in a more acidic solution.)
- absorbing excess hydrogen or hydroxide ions (Correct. Buffers work to minimize changes in either ion’s concentration.)
A: absorbing excess hydrogen or hydroxide ions

Q: ________ in the body affect blood pH by creating bicarbonate when the pH needs to be lowered.
- Acids (Incorrect. Acids do not create bicarbonate.)
- Bases (Incorrect. Bases do not work to lower pH.)
- Buffers (Correct. Buffers will work to stabilize the pH in whatever direction is needed.)
A: Buffers

Q: A common household example of a buffer is ________.
- bleach (Incorrect. This is a base.)
- lemon juice (Incorrect. This is an acid.)
- antacid (Correct. This is a buffer designed to modulate stomach acid pH in particular.)
A: antacid

Q: Ultimately, excess ________ build up in the body is prevented by the exhalation of carbon dioxide.
- bicarbonate (Incorrect. Bicarbonate is used as a buffer in the body, and is not removed by exhalation of carbon dioxide.)
- hydrogen atoms (Incorrect. Hydrogen atoms are neutral and have no impact on pH, nor will they build up in the body.)
- hydrogen ions (Correct. This prevents build up of carbonic acid specifically.)
A: hydrogen ions