Question

vii. posttest

1. chlorine has an atomic number of 17. how many electrons are in the outermost shell?

a. one
b. seven
c. eight
d. it varies

1. when chlorine becomes the chloride ion, its charge is

a. plus one
b. plus seven
c. minus one
d. minus seven

1. when hydrogen chloride, a strong acid, is added to water, the ph

a. goes up
b. stays the same
c. goes down
d. cannot be determined

1. when two nonmetal oxygen (#8) atoms react with each other, they

a. each give up two electrons
b. each take two electrons
c. each need six electrons
d. share

1. in this reaction, k + cl → k+cl−, chlorine has been reduced.

a. true
b. false

1. this bond o h - c - n - between the carbon and nitrogen is a

a. hydrogen bond
b. weak bond
c. peptide bond
d. all of these

1. which one molecule would be used repeatedly to form a nucleic acid?

a. nucleotide
b. amino acid
c. glucose
d. any one of these

1. the backbone of a nucleic acid would be composed of

a. the bases
b. sugar - phosphate - sugar - phosphate, etc.
c. n - c - c - n - c - c - n - c - c - n
d. the “r” groups

1. which molecule is unsaturated?

a. h - c - c - c - c - h h h h o h
b. h - c - c = c - c - h h h h o h

Explanation:

1. Chlorine (atomic number 17) has electron configuration 2,8,7; outer shell has 7 electrons.
2. Chlorine gains 1 electron to form Cl⁻, charge is -1.
3. Strong acid increases H⁺, lowering pH.
4. Nonmetals (O) share electrons in covalent bonding.
5. Cl gains an electron (reduction), so statement is true.
6. -C(=O)-N- is the peptide bond linking amino acids.
7. Nucleic acids are polymers of nucleotides.
8. Nucleic acid backbone is sugar-phosphate repeating units.
9. Unsaturated molecules have double bonds; option b has C=C.

Answer:

1. b. seven
2. c. minus one
3. c. goes down
4. d. share
5. a. True
6. c. peptide bond
7. a. nucleotide
8. b. sugar-phosphate-sugar-phosphate, etc.
9. b. H—C—C=C—C—H (with the structure shown)