Introductory Chemistry, 5e (Tro)
Chapter 5 Molecules and Compounds
True/False Questions
1) When elements combine to form compounds, their properties only change slightly.
2) The properties of a compound are an average of the properties of the individual elements.
3) Life could not exist with just 91 elements if they did not combine to form compounds.
4) Although some substances we encounter in our routine lives are elements, most occur in the
combined state.
5) The law of constant composition states: All samples of a given compound have the same
proportions of their constituent elements.
6) The fact that water has an oxygen-to-hydrogen mass ratio of 8.0 illustrates the law of
conservation of mass.
7) The ratio in a chemical formula is a ratio of atoms, not a ratio of masses.
8) The subscripts in a chemical formula represent the relative mass of each atom in a chemical
compound.
9) The subscripts in a chemical formula do not change for a given compound.
10) Chemical formulas normally list the most metallic elements first.
11) The formula of a compound comprised of two nitrogen atoms and one oxygen atom should
be written properly as ON2.
12) Molecular elements do not exist in nature.
13) The element nitrogen normally exists in nature as a diatomic molecule.
14) If a chemical reaction produces the molecular element oxygen, the formula of oxygen should
be written as O2 .
15) Carbon dioxide is an example of a molecular compound.
16) The basic unit of an ionic compound is called the formula unit.
17) SO2 is an ionic compound.
18) Ionic compounds have a net charge of zero.
19) Ionic compounds always contain positive and negative ions.
20) In ionic compounds the net positive charge always equals the net negative charge.
21) The ionic compound that forms between aluminum and oxygen is AlO.
22) The ionic compound that forms between Mg and O is MgO.
23) The correct formula for calcium fluoride is CaF3.
24) Ionic compounds are usually made up of a metal and a nonmetal.
25) The ionic compound MgO is named manganese oxide.
26) The name of KNO3 is potassium nitratide.
27) The correct formula for sodium permanganate is NaMgO4.
28) Metal cations that form more than one type of ion are usually found in the section of the
periodic table known as the transition metals.
29) If there are two ions in a series of oxoanions, the one with more oxygen is given the ending
“-ite.”
30) The proper name for SF6 is sulfur tetrafluoride.
31) The proper name for the acid HF is hydrofluoric acid.
32) The proper name for HI is hydroiodic acid.
33) The correct name for HNO3 is hydronitric acid.
34) Carbonic acid, H2CO3 , contains the carbonate oxyanion.
35) If an oxyacid contains the sulfate oxyanion, then this acid has the name sulfurous acid.
36) The correct name for H2SO3 is sulfurous acid.
Multiple Choice Questions
1) When elements combine to form compounds:
A) their properties are an average of all elements in the compound.
B) their properties change completely.
C) their properties do not change.
D) their properties are completely random.
E) none of the above
2) The first chemist to formally state the law of constant composition was:
A) Dalton.
B) Mendeleev.
C) Rutherford.
D) Proust.
E) none of the above
3) The law of constant composition states:
A) Matter cannot be either created or destroyed in a chemical reaction.
B) The nucleus is a dense region of positive charge that always contains protons and neutrons.
C) All samples of a given compound have the same proportions of their constituent elements.
D) All atoms of a given element have a constant composition and are different than atoms of any
other element.
E) none of the above
4) The oxygen-to-hydrogen mass ratio of water is always 8.0 is an example of what fundamental
law?
A) Law of Constant Composition
B) Law of Constant Mass Ratio
C) Law of Conservation of Mass
D) Law of Constant Whole Number Ratio
E) none of the above
5) What is the oxygen-to-hydrogen mass ratio for H2O2?
A) 0.125
B) 4
C) 8
D) 16
E) none of the above
6) The phosphorous-to-hydrogen mass ratio is 10.2 for a compound. This ratio could correspond
to the compound:
A) PH.
B) PH2.
C) PH3.
D) PH6.
E) none of the above
7) What is the oxygen-to-sulfur mass ratio of sulfur dioxide?
A) 0.5
B) 1.0
C) 2.0
D) 16
E) none of the above
8) Suppose an unknown compound XY has an X-to-Y mass ratio of 4.0. If decomposition of
compound XY gives 12.0 grams of X, then how many grams of Y must form?
A) 48.0 grams
B) 12.0 grams
C) 4.0 grams
D) 3.0 grams
E) none of the above
9) Which of the following statements about chemical formulas is FALSE?
A) The subscripts represent the relative number of each type of atom in the compound.
B) The subscripts represent the relative mass of each type of atom in the compound.
C) The subscripts do not change for a given compound.
D) Different compounds made of the same elements have different subscripts.
E) All of the statements are true.
10) How many total atoms are in the formula Al2(CO3)3?
A) 8
B) 9
C) 12
D) 14
E) none of the above
11) How many carbon atoms are in the formula Al2(CO3)3?
A) 3
B) 9
C) 1
D) 6
E) none of the above
12) How many oxygen atoms are in the formula Al2(CO3)3?
A) 3
B) 9
C) 1
D) 6
E) none of the above
13) Which formula shows the proper use of parentheses?
A) Ca(F)2
B) Ca(SO4)
C) (NH4)3(PO4)
D) Ca(NO3)2
E) none of the above
14) How many of each type of atoms are there in the formula NH4C2H3O2?
A) N = 4, H = 7, C = 2, O = 2
B) N = 1, H = 4, C = 2, O = 2
C) N = 1, H = 3, C = 2, O = 2
D) N = 1, H = 7, C = 2, O = 2
E) none of the above
15) How many of each type of atom are there in the formula Ca3(PO4)2?
A) Ca = 3, P = 1, O = 4
B) Ca = 3, P = 2, O = 4
C) Ca = 3, P = 2, O = 8
D) Ca = 3, P = 1, O = 8
E) none of the above
16) How many of each type of atom are there in the formula (NH4)2HPO4?
A) N = 2, H = 9, P = 1, O = 4
B) N = 1, H = 5, P = 1, O = 4
C) N = 2, H = 5, P = 1, O = 4
D) N = 2, H = 8, P = 1, O = 4
E) none of the above
17) What is the correct formula for a compound that has three oxygen atoms and one sulfur
atom?
A) O3S
B) SO3
C) 3OS
D) SO3
E) none of the above
18) What is the correct formula of a compound that has ten oxygen atoms and four phosphorus
atoms?
A) O10P4
B) 10OP4
C) 4PO10
D) P4O10
E) none of the above
19) Carbon is considered which of the following?
A) atomic element
B) molecular element
C) molecular compound
D) ionic compound
E) none of the above
20) Which among the following elements does NOT exist as a diatomic molecule in nature?
A) hydrogen
B) nitrogen
C) fluorine
D) neon
E) none of the above
21) Carbon monoxide is considered which of the following?
A) atomic element
B) molecular element
C) molecular compound
D) ionic compound
E) none of the above
22) Fluorine is considered which of the following?
A) atomic element
B) molecular element
C) molecular compound
D) ionic compound
E) none of the above
23) Ammonium fluoride is considered which of the following?
A) atomic element
B) molecular element
C) molecular compound
D) ionic compound
E) none of the above
24) Which of the following species is a molecular element?
A) neon
B) sodium
C) chlorine
D) carbon dioxide
E) none of the above
25) Which of the following is a molecular compound?
A) barium sulfide
B) calcium acetate
C) potassium hydroxide
D) nitrogen monoxide
E) none of the above
26) What is the formula for an ionic compound made of barium and nitrogen?
A) Ba3N2
B) Ba2N3
C) BaN
D) Ba2N4
E) none of the above
27) What is the formula for an ionic compound made of magnesium and sulfur?
A) MgS
B) MgS2
C) Mg2S
D) Mg2S3
E) none of the above
28) What is the formula for an ionic compound made of carbon and oxygen?
A) CO2
B) C2O
C) CO
D) CO3
E) Carbon and oxygen do not form an ionic compound.
29) The ionic compound that forms between potassium and oxygen is:
A) K2O.
B) KO.
C) KO2.
D) K2O2.
E) none of the above
30) What is the formula for an ionic compound made of aluminum and oxygen?
A) AlO2
B) Al2O3
C) Al3O2
D) AlO
E) none of the above
31) A student wrote the formula for the compound aluminum phosphate as AlPO4 . What is
wrong with this formula?
A) The compound is not charge-neutral.
B) Aluminum is a nonmetal so it cannot form an ionic compound.
C) The formula should be Al(PO4) .
D) There cannot be three different atom types in a chemical formula.
E) Nothing is wrong with the formula.
32) What is the name of the ionic compound made of beryllium and chlorine?
A) beryllium(II) chloride
B) beryllium dichloride
C) beryllium chloride
D) monoberyllium dichloride
E) none of the above