Chapter 2 Test

Which of the following is TRUE of atomic weight?

Atomic weight of an element is approximately equal to the mass number of its most abundant isotope. Correct Atomic weight is an average of the relative weights (mass numbers) of all the isotopes of an element, taking into account their relative abundance in nature. As a rule, the atomic weight of an element is approximately equal to the mass number of its most abundant isotope.

Suspensions may also be called emulsions. True False

False Correct Colloids, not suspensions may also be called emulsions. Colloids are heterogeneous mixtures, meaning their composition is dissimilar in different areas of the mixture. Colloids often appear translucent or milky and although the solute particles are larger than those in true solutions, they still do not settle out. Suspensions are heterogeneous mixtures with large, often visible solutes that tend to settle out.

Organic compounds are covalently bonded and they always contain oxygen. True False

False Correct Organic compounds are covalently bonded and they always contain carbon; they often contain oxygen as well.

Nonpolar molecules are the result of unequal electron pair sharing. True False

False Correct Polar molecules are the result of unequal electron pair sharing. Nonpolar molecules are electrically balanced due to the equal sharing of electrons between the atoms of the molecules.

Atomic number is equal to the number of neutrons in an atom's nucleus. True False

False Correct The atomic number of any atom is equal to the number of protons, not neutrons, in its nucleus.

Which of the following is NOT one of the three major types of chemical reactions? decomposition hyperbolic synthesis exchange

Hyperbolic Correct Most chemical reactions exhibit one of three recognizable patterns. They are either synthesis, decomposition, or exchange reactions.

What is the difference between kinetic and potential energy?

Kinetic energy is energy in action, while potential energy is stored energy. Correct Kinetic energy is energy in action. We see evidence of kinetic energy in the constant movement of the tiniest particles of matter, as well as in larger objects. Potential energy is stored energy, which has the capacity to do work, but is not presently doing so.

Which of the following is NOT a difference between a compound and a mixture? Mixtures are homogeneous while compounds are heterogeneous. Mixtures can be separated by physical means, for example, straining, filtering, or evaporation. Compounds can only be separated into their constituent atoms by chemically breaking bonds. No chemical bonding occurs between the components of a mixture. The properties of atoms and molecules are not changed when they become part of a mixture. Some mixtures are homogenous, while others are heterogeneous. All compounds are homogeneous.

Mixtures are homogeneous while compounds are heterogeneous. Correct Mixtures differ from compounds in several important ways. (1) The chief difference between mixtures and compounds is that no chemical bonding occurs between the components of a mixture. The properties of atoms and molecules are not changed when they become part of a mixture. (2) Depending on the mixture, its components can be separated by physical means, straining, filtering, evaporation, and so on. Compounds, by contrast, can be separated into their constituent atoms only by chemical means (breaking bonds). (3) Some mixtures are homogenous, while others are heterogeneous. All compounds are homogeneous.

Which of the following is NOT a subatomic particle? proton electron molecule neutron

Molecule Correct Atoms are comprised of subatomic particles: protons, electrons and neutrons. Most atoms do not exist in the free state, but instead are chemically combined with other atoms. Such a combination of two or more atoms held together by chemical bonds is called a molecule.

Which of the following best describes an isotope?

Structurally variant atoms, which have the same number of protons and electrons, but differ in the number of neutrons they contain Correct Nearly all known elements have two or more structural variations called isotopes, which have the same number of protons and electrons, but differ in the number of neutrons they contain.

Which of the following best defines covalent bonds?

The bond formed when shared electrons occupy a single orbital common to both atoms within a molecule Correct Electron sharing produces molecules in which the shared electrons occupy a single orbital common to both atoms, which constitutes a covalent bond.

Which of the following is TRUE regarding the pH of a solution? The fewer hydroxyl ions in a solution, the more basic the solution is. The fewer hydrogen ions in a solution, the more acidic the solution is. The more hydroxyl ions in a solution, the more acidic the solution is. The more hydrogen ions in a solution, the more acidic the solution is.

The more hydrogen ions in a solution, the more acidic the solution is. Correct The more hydrogen ions in a solution, the more acidic the solution is.

Which of the following is NOT one of the three basic steps involved in enzyme activity? The substrate absorbs chemical energy from the enzyme after binding to its active site. The enzyme's active site binds to the substrate(s) on which it acts, temporarily forming an enzyme-substrate complex. The enzyme releases the product(s) of the reaction. The enzyme-substrate complex undergoes internal rearrangements that form the product(s).

The substrate absorbs chemical energy from the enzyme after binding to its active site. Correct Enzymes do not provide energy to their substrates. In fact, enzymes are completely unchanged by their catalytic role and can act again and again.

Which of the following is FALSE? Matter exists in solid, liquid, and gaseous states. With some exceptions, matter can be seen, smelled, and felt. The weight of matter remains constant wherever it is located. The mass of matter remains constant wherever it is located.

The wight of matter remains constant wherever it is located. Correct The mass of an object is equal to the actual amount of matter in the object, and it remains constant wherever the object is. In contrast, weight varies with gravity. Matter is anything that occupies space and has mass. With some exceptions, it can be seen, smelled and felt. Matter exists in solid, liquid, or gaseous states.

What are the two fundamental roles of DNA?

To provide the instructions for protein synthesis, and replicate itself before cell division Correct DNA has two fundamental roles: (1) to replicate itself before the cell divides, ensuring that all genetic information in the descendant cells is identical; and (2) to provide the basic instructions for building every protein in the body.

ATP is an unstable, high-energy molecule that provides body cells with a form of energy that is immediately usable. True False

True Correct ATP is the primary energy-transferring molecule in cells, and it provides a form of energy that is immediately usable by all body cells. Chemically, the triphosphate tail of ATP can be compared to a tightly coiled spring ready to uncoil with tremendous energy when the catch is released. Actually, ATP is a very unstable high-energy molecule because its three negatively charged phosphate groups are closely packed and repel each other.

Buffers help to stabilize blood pH. True False

True Correct Buffers are essential for stabilizing the pH of body fluids (such as blood). Note: buffers cannot prevent a change in pH, they can only resist or minimize the change (if acids or bases are added to the buffered solution).

The major function of RNA is to carry out the genetic instructions for protein synthesis. True False

True Correct The major function of RNA is to carry out the genetic instructions (provided by DNA) for protein synthesis.

Water ________.

can form hydrogen bonds Correct Due to its polar nature, water is able to form hydrogen bonds. In fact, many of the special properties of water derive from its extensive hydrogen bonding capacity. In addition, water has a high heat capacity and is considered a universal solvent since it dissolves more substances than any other known solvent.

Which four elements comprise approximately 96% of our body weight?

carbon, oxygen, hydrogen, and nitrogen. Correct Four elements: carbon, oxygen, hydrogen, and nitrogen make up about 96 percent of our body weight; 20 others are present in the body, some in trace amounts.

Which of the following forms of energy travels in varying wavelengths, such as visible light, infrared waves, radio waves, ultraviolet waves, and X-rays?

electromagnetic energy Correct Radiant energy, or electromagnetic energy, travels in waves. These waves, which vary in length, are collectively called the electromagnetic spectrum. They include visible light, infrared waves, radio waves, ultraviolet waves, and X rays.

The pH scale ________.

is based on the concentration of hydrogen ions in a solution Correct The pH scale, which ranges from 0 to 14, is a logarithmic scale based on the concentration of hydrogen ions in a solution.

Choose the correctly matched pair. amino acid: carbohydrate monosaccharide: lipid nucleotide: DNA glycerol and fatty acids: RNA

nucleotide: DNA Correct DNA and RNA are nucleic acids; they are built from nucleotides.