CHEM 101 PRACTICE EXAM
QUESTIONS AND DETAILED
SOLUTIONS 2026
▶ which of the following are chemical changes?
a) silver teapot turns black
b) candle wax is melted
c) candle is burned
d) two clear colorless salt sols are mixed and a bright orange precipitate
forms
e) sugar crystals ground to a fine powder. Answer: a) silver teapot turns
black
c) candle is burned
d) two clear colorless salt sols are mixed and a bright orange precipitate
forms
▶ what is the chemical formula for water. Answer: H2O
▶ periodic law. Answer: properties repeat within groups
elements arranged by atomic number
▶ atoms. Answer: Smallest particle of an element that still retains all
properties of that element
have 3 parts: protons, neutrons, electrons
▶ charge of proton. Answer: +1 charge, mass= 1 amu
▶ charge of neutron. Answer: no charge, mass= 1 amu
▶ charge of electron. Answer: -1 charge, mass= 0 amu
▶ electron model. Answer: old model: orbiting electrons
new model: electron cloud (contains all electrons)
▶ nucleus. Answer: all the protons and neutrons
, small volume
contains most of mass
▶a
X atomic symbol
z. Answer: a = mass number (p+n)
z = atomic number (p), *a-z=neutrons*
▶6
C periodic table
12.01. Answer: 6 = atomic number (periodic table arranged by this)
12.01 = average atomic mass
▶ elements are neutral. Answer: number of protons = number of electrons
▶ isotopes. Answer: Atoms with the same number of protons but different
numbers of neutrons
Properties determined by # of protons
▶ ions. Answer: atoms with a charge
-caused by different number of electrons
(-) = anion (electrons actually missing but taking away negative so # will go
up)
(+) = cation (CATion = PAWsitive) (electrons actually gained but is adding
a negative so # will go down)
▶ How many electrons in O^-2. Answer: 8
O two more e- = 10e-
16
▶ How many e- in sodium?. Answer: 11 <-- 11 protons, 11 electrons if
neutral
Na
22.99
Na has a +1 charge on periodic table, so = 10e-
▶ electron shells. Answer: n=3 18e-
n= 2 8e-
n = 1 2e-
QUESTIONS AND DETAILED
SOLUTIONS 2026
▶ which of the following are chemical changes?
a) silver teapot turns black
b) candle wax is melted
c) candle is burned
d) two clear colorless salt sols are mixed and a bright orange precipitate
forms
e) sugar crystals ground to a fine powder. Answer: a) silver teapot turns
black
c) candle is burned
d) two clear colorless salt sols are mixed and a bright orange precipitate
forms
▶ what is the chemical formula for water. Answer: H2O
▶ periodic law. Answer: properties repeat within groups
elements arranged by atomic number
▶ atoms. Answer: Smallest particle of an element that still retains all
properties of that element
have 3 parts: protons, neutrons, electrons
▶ charge of proton. Answer: +1 charge, mass= 1 amu
▶ charge of neutron. Answer: no charge, mass= 1 amu
▶ charge of electron. Answer: -1 charge, mass= 0 amu
▶ electron model. Answer: old model: orbiting electrons
new model: electron cloud (contains all electrons)
▶ nucleus. Answer: all the protons and neutrons
, small volume
contains most of mass
▶a
X atomic symbol
z. Answer: a = mass number (p+n)
z = atomic number (p), *a-z=neutrons*
▶6
C periodic table
12.01. Answer: 6 = atomic number (periodic table arranged by this)
12.01 = average atomic mass
▶ elements are neutral. Answer: number of protons = number of electrons
▶ isotopes. Answer: Atoms with the same number of protons but different
numbers of neutrons
Properties determined by # of protons
▶ ions. Answer: atoms with a charge
-caused by different number of electrons
(-) = anion (electrons actually missing but taking away negative so # will go
up)
(+) = cation (CATion = PAWsitive) (electrons actually gained but is adding
a negative so # will go down)
▶ How many electrons in O^-2. Answer: 8
O two more e- = 10e-
16
▶ How many e- in sodium?. Answer: 11 <-- 11 protons, 11 electrons if
neutral
Na
22.99
Na has a +1 charge on periodic table, so = 10e-
▶ electron shells. Answer: n=3 18e-
n= 2 8e-
n = 1 2e-
