Chapter 2

What coefficients must be placed in the following blanks so that all atoms are accounted for in the products? C6H12O6 S _____ C2H6O + _____ CO2 1; 1 1; 2 1; 3 2; 2 3; 1

2; 2

We can represent atoms by listing the number of protons, neutrons, and electrons-for example, 2p+, 2n0, 2e- for helium. Which of the following represents the 18O isotope of oxygen? 9p+, 9n0, 9e- 6p+, 8n0, 6e- 7p+, 2n0, 9e- 10p+, 8n0, 9e- 8p+, 10n0, 8e-

8p+, 10n0, 8e-

The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound. H3S2 H4S HS2 H2S HS

H2S

Which statement is true of all atoms that are anions? The net charge is 1-. The atom has more electrons than protons. The atom has fewer protons than does a neutral atom of the same element. The atom has more neutrons than protons. The atom has more protons than electrons.

The atom has more electrons than protons.

Which of the following statements correctly describes any chemical reaction that has reached equilibrium? The concentrations of products and reactants are equal. The rates of the forward and reverse reactions are equal. Both forward and reverse reactions have halted. The reaction is now irreversible. No reactants remain.

The rates of the forward and reverse reactions are equal.

Compared with 31P, the radioactive isotope 32P has a different atomic number. one more electron. one more proton. a different charge. one more neutron.

one more neutron.

In the term trace element, the adjective trace means that the element is very rare on Earth. the element enhances health but is not essential for the organism's long-term survival. the element passes rapidly through the organism. the element can be used as a label to trace atoms through an organism's metabolism. the element is required in very small amounts.

the element is required in very small amounts.

The reactivity of an atom arises from the sum of the potential energies of all the electron shells. the potential energy of the valence shell. the average distance of the outermost electron shell from the nucleus. the energy difference between the s and p orbitals. the existence of unpaired electrons in the valence shell.

the existence of unpaired electrons in the valence shell.