Chapter 2: Water and Carbon: The Chemical Basis of Life Flashcards
Atoms of a specific element always have a constant number of _____.
a) neutrons
b) isotopes
c) protons
d) Electrons
c) protons
Which of the following four elements make up 96 percent of matter found in living organisms?
a) sulfur, hydrogen, oxygen, and nitrogen
b) carbon, sulfur, nitrogen, and iron
c) hydrogen, carbon, oxygen, and sulfur
d) hydrogen, carbon, oxygen, and nitrogen
d) hydrogen, carbon, oxygen, and nitrogen
An element in the second row of the periodic table that has four valence electrons would most likely _____.
a) have a full outer shell and be unreactive
b) form ionic bonds
c) form four covalent bonds
d) be more electronegative than an element with six valence electrons in the same row of the periodic table
c) form four covalent bonds
Which of the following is necessary for an atom to participate in the formation of a double covalent bond?
a) There has to be a difference in electronegativity between it and the atom with which it forms the double covalent bond.
b) The participating atoms must have two or more unpaired electrons.
c) The participating atoms must have a full outer shell.
d) The participating atoms must have two or more valence electrons.
b) The participating atoms must have two or more unpaired electrons.
The electron-sharing continuum represents the degree to which electrons are shared in chemical bonds by showing that _____.
a) atoms with no charge transfer electrons with atoms with full charge
b) atoms with full charges transfer electrons and form ionic bonds
c) atoms with partial charges form nonpolar covalent bonds and share electrons equally
d) atoms with a full charge form nonpolar covalent bonds and share electrons equally
b) atoms with full charges transfer electrons and form ionic bonds
Unlike an anion, a cation has a(n) _____.
a) neutral charge
b) electric charge
c) negative charge
d) positive charge
d) positive charge
Which of the following best describes why ionic molecules dissolve and dissociate in water?
a) Water is hydrophobic.
b) Water is a polar, covalently bonded substance.
c) Water is liquid at room temperature.
d) Water is formed from nonpolar covalent bonds between oxygen and hydrogen.
b) Water is a polar, covalently bonded substance.
Water has a high capacity for energy absorption, surface tension, and functioning effectively as a solvent for polar covalently bonded and ionically bonded molecules. What feature of water imparts these properties?
a) Water readily forms hydrogen bonds with other water molecules and with polar solutes.
b) The hydrogen and oxygen that make up water form nonpolar covalent bonds.
c) Water readily dissociates to form H+and OH− ions.
d) Water has a high molecular weight.
a) Water readily forms hydrogen bonds with other water molecules and with polar solutes.
An acid is defined by which of the following?
a) It is insoluble in water.
b) It has a high pH value.
c) It accepts protons from other elements in a solution.
d) It donates protons to other substances in a solution.
d) It donates protons to other substances in a solution.
What is the significance of buffers in biological systems?
a) They are usually involved in chemical reactions that result in energy production.
b) They help maintain homeostasis with respect to pH.
c) They are not present and are therefore insignificant in biological systems.
d) They help maintain a constant temperature in biological systems.
b) They help maintain homeostasis with respect to pH.
As an example of a(n) _____, household bleach can be characterized as having a _____.
a) base; pH greater than 7
b) base; pH less than 7
c) neutral solution; pH of 7
d) acid; proton concentration larger than 1 × 10^−7 M
a) base; pH greater than 7
In the chemical equation for burning methane (CH4 + O2 → CO2 + H2O), CH4 and O2 are the _____ and CO2 and H2O are the _____.
a) anions; cations
b) products; reactants
c) molecules; atoms
d) reactants; products
d) reactants; products
A large boulder is balanced on the top of a hill. You give the boulder a push, and it rolls down the hill. This is an example of converting _____ energy to _____ energy.
a) kinetic; potential
b) chemical; kinetic
c) potential; kinetic
d) kinetic; thermal
c) potential; kinetic
An iceberg near the Arctic Circle represents which unusual property of water?
a) its higher density as a liquid than as a solid
b) its high specific heat
c) its heat of vaporization
d) its effectiveness as a solvent
a) its higher density as a liquid than as a solid
Which factor most accurately defines whether or not a chemical reaction is spontaneous?
a) pH of reactants or products
b) difference in energy level between products and reactants
c) degree of entropy (disorder in a group of molecules)
d) temperature of products and reactants
b) difference in energy level between products and reactants
