Actual Chemistry Practice Test HESI A2
Exam BEST RATED SOLUTION 2025
questions and correct answers
upgraded to 2026 graded A+
Which postulate(s) of Dalton's atomic theory of matter is/are
NOT true?
A) Atoms of a given element are identical
B) Atoms are indestructible
C) Atoms combine in simple ratios to form compounds
D) Both (A) and (B)
D. Both A and B
Which scientist determined the charge of the electron?
A) John Dalton
B) J. J. Thomson
C) Robert Millikan
D) Ernest Rutherford
E) James Chadwick
C. Robert Milikan
Rutherford's gold foil experiment determined that
A) neutrons are in the nucleus.
B) electrons have a negative charge.
C) most of the space in an atom is empty except for a
concentrated area called the nucleus.
D) protons and neutrons have about the same mass.
E) neutrons have no charge.
C. most of the space in an atom is empty except for a
concentrated area called the nucleus.
What does the mass number of an atom represent?
A) number of neutrons in the atom
B) number of protons in the atom
,C) atomic mass of the element
D) total number of electrons and neutrons in the atom
E) total number of protons and neutrons in the atom
E. Total number of protons and neutrons in the atom
The nucleus of an atom contains:
A) Protons and electrons
B) Protons and neutrons
C) Electrons and neutrons
D) Protons, neutrons and electrons
E) Electrons only
B. Protons and neutrons
Which two particles of the atom have nearly identical
masses?
A) Proton and electron
B) Proton and neutron
C) Neutron and electron
D) No two particles have similar masses
B. Proton and neutron
What element with a mass number of 100 has 56 neutrons in
its nucleus?
A) Fermium (Fm)
B) Ruthenium (Ru)
C) Barium (Ba)
D) Copernicium (Cn)
E) Radium (Ra)
B. Ruthenium
How many protons are in an atom of Co?
27
What is the mass number for an atom of xenon containing 54
protons and 75 neutrons?
129
The atomic mass of germanium (Ge) on the periodic table is
72.630 amu. Which of the following best explains why the
atomic mass is a fraction between 72 and 73?
A) The presence of different isotopes
,B) The presence of different isomers.
C) The formation of different ions.
D) The presence of different allotropes.
E) The presence of different amounts of protons.
A. The presence of different isotopes
An unknown element X has the following isotopes: ²⁵X (80.5%
abundant) and ²⁷X (19.5% abundant). What is the average
atomic mass in amu of X?
25.4 amu
The empirical formula of a covalent compound is CH₂. Which
of the following is NOT a possible chemical formula for this
compound?
A) C₅H₁₀
B) C₇H₁₄
C) C₆H₁₀
D) C₄H₈
E) C₃H₆
C. C6H10
Glucose is an important biological molecule with the
molecular formula C₆H₁₂O₆. What is its empirical formula?
A) CHO
B) CH₂O
C) C₂HO₂
D) C₆H₁₂O₆
E) Not enough info
B. CH2O
How many oxygen atoms are in 25 molecules of dinitrogen
tetroxide, N₂O₄?
100 atoms
Columns on the periodic table are known as
A) Periods
B) Halogens
C) Metals
D) Groups
E) Metalloids
, D. Groups
The symbol Cd represents the element _____
A) carbon
B) calcium
C) cadmium
D) californium
E) cesium
C. Cadmium
The halogens are found in Group ____
A) 1A (1)
B) 2A (2)
C) 6A (16)
D) 7A (17)
E) 8A (18)
D. 7A(17)
The element symbol for potassium is _____
A) P
B) Po
C) K
D) Kr
E) Pa
C.K
Which of the following is a main group element?
A) Yttrium
B) Osmium
C) Holmium
D) Californium
E) Bismuth
E. Bismuth
Which of the following sets of elements and symbols is
paired correctly?
A) rubidium, Ru
B) indium, In
C) thallium, Tm
Exam BEST RATED SOLUTION 2025
questions and correct answers
upgraded to 2026 graded A+
Which postulate(s) of Dalton's atomic theory of matter is/are
NOT true?
A) Atoms of a given element are identical
B) Atoms are indestructible
C) Atoms combine in simple ratios to form compounds
D) Both (A) and (B)
D. Both A and B
Which scientist determined the charge of the electron?
A) John Dalton
B) J. J. Thomson
C) Robert Millikan
D) Ernest Rutherford
E) James Chadwick
C. Robert Milikan
Rutherford's gold foil experiment determined that
A) neutrons are in the nucleus.
B) electrons have a negative charge.
C) most of the space in an atom is empty except for a
concentrated area called the nucleus.
D) protons and neutrons have about the same mass.
E) neutrons have no charge.
C. most of the space in an atom is empty except for a
concentrated area called the nucleus.
What does the mass number of an atom represent?
A) number of neutrons in the atom
B) number of protons in the atom
,C) atomic mass of the element
D) total number of electrons and neutrons in the atom
E) total number of protons and neutrons in the atom
E. Total number of protons and neutrons in the atom
The nucleus of an atom contains:
A) Protons and electrons
B) Protons and neutrons
C) Electrons and neutrons
D) Protons, neutrons and electrons
E) Electrons only
B. Protons and neutrons
Which two particles of the atom have nearly identical
masses?
A) Proton and electron
B) Proton and neutron
C) Neutron and electron
D) No two particles have similar masses
B. Proton and neutron
What element with a mass number of 100 has 56 neutrons in
its nucleus?
A) Fermium (Fm)
B) Ruthenium (Ru)
C) Barium (Ba)
D) Copernicium (Cn)
E) Radium (Ra)
B. Ruthenium
How many protons are in an atom of Co?
27
What is the mass number for an atom of xenon containing 54
protons and 75 neutrons?
129
The atomic mass of germanium (Ge) on the periodic table is
72.630 amu. Which of the following best explains why the
atomic mass is a fraction between 72 and 73?
A) The presence of different isotopes
,B) The presence of different isomers.
C) The formation of different ions.
D) The presence of different allotropes.
E) The presence of different amounts of protons.
A. The presence of different isotopes
An unknown element X has the following isotopes: ²⁵X (80.5%
abundant) and ²⁷X (19.5% abundant). What is the average
atomic mass in amu of X?
25.4 amu
The empirical formula of a covalent compound is CH₂. Which
of the following is NOT a possible chemical formula for this
compound?
A) C₅H₁₀
B) C₇H₁₄
C) C₆H₁₀
D) C₄H₈
E) C₃H₆
C. C6H10
Glucose is an important biological molecule with the
molecular formula C₆H₁₂O₆. What is its empirical formula?
A) CHO
B) CH₂O
C) C₂HO₂
D) C₆H₁₂O₆
E) Not enough info
B. CH2O
How many oxygen atoms are in 25 molecules of dinitrogen
tetroxide, N₂O₄?
100 atoms
Columns on the periodic table are known as
A) Periods
B) Halogens
C) Metals
D) Groups
E) Metalloids
, D. Groups
The symbol Cd represents the element _____
A) carbon
B) calcium
C) cadmium
D) californium
E) cesium
C. Cadmium
The halogens are found in Group ____
A) 1A (1)
B) 2A (2)
C) 6A (16)
D) 7A (17)
E) 8A (18)
D. 7A(17)
The element symbol for potassium is _____
A) P
B) Po
C) K
D) Kr
E) Pa
C.K
Which of the following is a main group element?
A) Yttrium
B) Osmium
C) Holmium
D) Californium
E) Bismuth
E. Bismuth
Which of the following sets of elements and symbols is
paired correctly?
A) rubidium, Ru
B) indium, In
C) thallium, Tm
