HESI A2 Chemistry Practice Test

Below is our free HESI A2 Chemistry practice test, which includes 40 challenging practice questions. It’s very important for all healthcare professionals to have a solid understanding of chemistry to help them provide safe and effective care. These HESI Chemistry practice questions are designed to cover the major concepts found on the test. Chemistry can be a difficult topic, so start your test prep right now with our free practice test.

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Question 1
An unknown element is found to contain 45 protons and an atomic mass of 64, what is its atomic number?

A
It cannot be determined.
B
19
C
45
D
64
Question 1 Explanation: 
The number of protons in an atom’s nucleus is also the atomic number of the atom. In this case, we are told that there are 45 protons present and that the atomic mass is 64; however, when looking for the atomic number, we do not need the atomic mass. Consequently, the atomic number is 45.
Question 2
Elements that are in the same column of the periodic table are in the same:

A
period.
B
group.
C
row.
D
classification.
Question 2 Explanation: 
Elements in the same horizontal row are in the same period, and they have similar physical properties. Elements in the same vertical column are in the same group, and they react to other elements in similar ways. There are 7 periods and 18 groups.
Question 3
What is the purpose of scientific notation?

A
There is no purpose.
B
The purpose is to handle bigger numbers more easily.
C
The purpose is to handle smaller numbers more easily.
D
The purpose is to handle both smaller and bigger numbers more easily.
Question 3 Explanation: 
Scientific notation allows us to better describe tiny and enormous numbers more easily.
Question 4
What is the metric prefix meaning one billionth?

A
Nano
B
Milli
C
Micro
D
Pico
Question 4 Explanation: 
The common metric prefixes for numbers less than 1 are as follows:

deci = tenth
centi = hundredth
milli = thousandth
micro = millionth
nano = billionth
pico = trillionth
Question 5
A normal human body temperature in Celsius is:

A
32 degrees.
B
35 degrees.
C
37 degrees.
D
39 degrees.
Question 5 Explanation: 
The normal human temperature in Celsius ranges from 36.5 to 37.5 degrees, so 37 degrees is the best answer.
Question 6
Which of the following statements about atoms is false?

A
Electrons do not orbit an atom’s nucleus; they exist in electron clouds surrounding the nucleus.
B
As each orbital of an atom is filled to capacity, electrons begin occupying a higher energy orbital.
C
Most of the volume of an atom is empty space.
D
Atoms are most stable when their outer electron shell (valence shell) is incomplete.
Question 6 Explanation: 
Atoms are most stable when they have a full outer electron orbit or shell. Incomplete orbits are more reactive.
Question 7
What are isotopes?

A
Elements which have the same number of protons but a different number of neutrons.
B
Elements with the same atomic number but different atomic mass numbers.
C
Elements which have a different number of protons than electrons.
D
Both A and B are correct.
Question 7 Explanation: 
Isotopes are the same element, with the same number of protons and electrons, but a different number of neutrons. Because there are different numbers of neutrons, the atomic masses of the elements also differ.
Question 8
What is the charge on sodium in the compound NaCl ?

A
−1
B
0
C
+1
D
+2
Question 8 Explanation: 
The chemical reaction between sodium and chlorine is ionic; Sodium donates an electron to chlorine to produce sodium chloride. The donation of an electron leaves sodium with a charge of +1 and chlorine with a charge of −1.
Question 9
A student is observing a chemical reaction occurring with visible bubbling. The bubbling eventually stops. The student can see that some of the original reactants are still intact inside the beaker, so he knows that not all the reactant has been used up. Therefore, the student knows he is now observing:

A
A failed reaction.
B
Equilibrium.
C
A decrease in temperature.
D
A completed reaction.
Question 9 Explanation: 
The student is now observing equilibrium, during which reactants are forming products at the same rate that products are forming reactants.
Question 10
Which of the following is the atomic mass of an atom containing 31 protons 31 electrons and 37 neutrons?

A
62
B
68
C
70
D
99
Question 10 Explanation: 
To calculate the atomic mass, sum the number of protons and the number of neutrons inside of the nucleus. The electron’s size is miniscule in comparison to both the proton and the neutron and does not contribute to the mass of the atom. So, adding 31 protons with 37 neutrons results in an atomic mass of 68.
Question 11
Fe + CuSO4 → FeSO4 + Cu is an example of what type of reaction?

A
Single Replacement
B
Combustion
C
Double Replacement
D
Decomposition
Question 11 Explanation: 
The reactants show that sulfate is bonded to copper, but the products show that the sulfate has bonded with the iron. As only the location of the sulfate has changed, this is a single replacement reaction. In order for this to be a combustion reaction, the products would need to be carbon dioxide and water. In order for it to be a double replacement reaction, there must be the replacement of two reactants; and in order for it to be decomposition, a reactant must be broken down into its constituent parts.
Question 12
Which of the following creates a cramping sensation during intense exercise?

A
Glucose.
B
Pyruvate.
C
Lactate.
D
Protein.
Question 12 Explanation: 
Lactate, also known as lactic acid, is responsible for the muscle burning or cramping feeling that accompanies intense exercise.
Question 13
DNA is made up of which of the following nucleotides?

A
Adenine, Guanine, Cytosine, and Thymine
B
Uracil, Adenine, Guanine, and Thymine
C
Amenine, Cytosine, Galvine, Thymine
D
Ribose, Phosphate, Pentose, and Amine
Question 13 Explanation: 
The information in DNA is stored as four nucleotides: adenine (A), guanine (G), cytosine (C), and thymine (T). The nucleotides adenine and guanine are classified as purines, while thymine and cytosine are classified as pyrmidines. Purines contain 2 carbon nitrogen ring bases and pyrimidines contain 1 carbon nitrogen base. These nucleotides can be easily remembered with the mnemonic, ‘GCAT PuPy PuPy,’ where ‘G’ and ‘A’ match up with ‘Pu’ (purine) and ‘C’ and ‘T’ match up with ‘Py’ (pyrimidine). RNA replaces thymine with uracil (U) and can be recalled as ‘GCAU PuPy PuPy.’
Question 14
What is the total number of sulfur atoms represented in 3 Ca(S04)3?

A
3
B
4
C
6
D
9
Question 14 Explanation: 
Sulfur is indicated by the symbol S and we are required to find the total number. Notice that the subscript 4 is only attached to the O atom so it will not be included in our calculation; however, the subscript 3 outside of the parenthesis will count. The coefficient 3 indicates that there are 3 total molecules, and each of these has 3 atoms of sulfur. Multiply: 3 x 3 = 9.
Question 15
The pH scale ranges from 0 to 14, where 0 is more _____ and 14 is more ______.

A
basic, acidic
B
neutral, acidic
C
acidic, neutral
D
acidic, basic
Question 15 Explanation: 
A pH of 0 is most acidic whereas a pH of 14 is most basic.
Question 16
Glycolysis results in a net gain of how many ATP molecules?

A
0
B
1
C
2
D
4
Question 16 Explanation: 
The reaction of glycolysis is the splitting of a glucose molecule into 2 pyruvic acid molecules. The reaction requires the contribution of 2 ATP molecules to start, but in the process liberates 2 molecules of ATP from each resulting pyruvate. Because the process results in 2 molecules of pyruvate, a total of 4 ATP molecules are freed, but because the reaction required 2 ATP molecules to start, the net gain in ATP is 2.
Question 17
Fluorine, oxygen, and nitrogen would each form what type of bond with a hydrogen atom?

A
Polar bond.
B
Covalent bond.
C
Hydrogen bond.
D
All of the above.
Question 17 Explanation: 
Fluorine, oxygen, and nitrogen are likely to form hydrogen bonds because they are each lacking electrons in their outer shell. Covalent bonds would form because hydrogen readily accepts single covalent bonds (sharing of its electron) and polar because hydrogen has a very low electronegativity compared to most elements.
Question 18
Which of the following is an example of a ionic bond?

A
NaCl
B
OH−
C
H3O+
D
COO−
Question 18 Explanation: 
NaCl is an example of an ionic bond because it does not have a charge, and because the reaction involves the gain and loss of an electron.
Question 19
What does -COOH symbolize?

A
Hydroxyl group
B
Carboxyl group.
C
Carbonyl group
D
Amino group
Question 19 Explanation: 
The carboxyl group has both a carbonyl and a hydroxyl group attached to the same carbon atom.
Question 20
Given enough time, unstable nuclei will:

A
lose protons.
B
evolve.
C
decay into a stable form.
D
degrade into a further unstable form.
Question 20 Explanation: 
Given enough time, unstable nuclei will decay into a stable form.
Question 21
The process by which silver nitrate and potassium chloride yields silver chloride and potassium nitrate is an example of which type of chemical reaction?

A
synthesis
B
combustion
C
double displacement
D
single displacement
Question 21 Explanation: 
This is an example of a double displacement reaction where the compounds have switched partners.
Question 22
A scientist discovers an atom of sodium in its natural state. The scientist knows that the oxidation number of this atom is most likely:

A
0.
B
1.
C
2.
D
3.
Question 22 Explanation: 
The oxidation number of most elements in their natural state is 0.
Question 23
How many glucose molecules are required to balance the following reaction:

_C6H12O6 + 24O2 → 24CO2 + 24H2O + Energy

A
4
B
8
C
16
D
24
Question 23 Explanation: 
For a chemical reaction to be balanced, the amount of reactants must be the same as the amount of products. Counting the number of carbon dioxide molecules on the right we find 24 total. As there are naturally 6 carbons in the glucose molecule on the left, we need 4 groups of these 6 molecules to match the 24 on the right.
Question 24
List these common radiation types from weakest to strongest in terms of penetrability: Alpha, Beta, and Gamma radiation.

A
Alpha, Beta, Gamma
B
Beta, Alpha, Gamma
C
Gamma, Beta, Alpha
D
Gamma, Alpha, Beta
Question 24 Explanation: 
Radiation strength can be gauged by the types of material that the radiation can pass through. Alpha radiation has the weakest depth of penetration and can be stopped by most surfaces. Beta radiation can penetrate more deeply than alpha radiation but not as deeply as gamma radiation. One can remember this ranking by thinking in terms of alphabetical order- alpha first, so weakest, beta next, so less weak, etc.
Question 25
A chemical drain cleaner that contains sodium hydroxide would be:

A
acidic.
B
alkaline.
C
neutral.
D
none of the above.
Question 25 Explanation: 
Sodium hydroxide has a pH in the range of 12-14, which is very basic, or alkaline. Alkaline drain cleaner can dissolve fats (grease) and proteins (hair).
Question 26
Which of the following subatomic particles are found inside of an atom’s nucleus?

A
Electrons, neutrons, protons
B
Neutrons, protons
C
Electrons, protons
D
Electrons
Question 26 Explanation: 
While the entirety of an atom’s nucleus contains neutrons, protons, and electrons, only the neutrons and protons are found inside of the nucleus. Electrons exist as a cloud surrounding the nucleus and thus are not found inside it.
Question 27
Which of the following saccharides are commonly associated with the sweet taste of fruit?

A
Glucose.
B
Fructose.
C
Lactose.
D
Galactose.
Question 27 Explanation: 
Fructose is a monosaccharide that makes fruit taste sweet. This can be easily remembered because fruit and fructose both begin with ‘fr’.
Question 28
Foods such as oils, milk, and butter contain high amounts of:

A
proteins.
B
carbohydrates.
C
calcium.
D
lipids.
Question 28 Explanation: 
These food products are all high in fats. Fats are a subgroup of lipids called triglycerides.
Question 29
DNA features two sugar-phosphate chains that run in opposite directions, with one up and one down. This characteristic is known as:

A
anti-parallel.
B
bilateral.
C
parallel.
D
bisecting.
Question 29 Explanation: 
Because the two chains run in opposite directions, they are described as anti-parallel.
Question 30
Which of the following is the correct description of stoichiometry?

A
Stoichiometry describes the chemical reactions between the elements of a compound.
B
Stoichiometry is the calculation of relative quantities of reactants and products in chemical reactions.
C
Stoichiometry describes the color flares expected based on the participants of a chemical reaction.
D
Stoichiometry describes the fundamental properties of atoms universally.
Question 30 Explanation: 
Stoichiometry deals with calculations of the masses of reactants and products involved in a chemical reaction. Stoichiometry is a mathematical part of chemistry.
Question 31
In a redox reaction, the element that is oxidized _____ an electron and the element that is reduced _____ an electron.

A
gains, loses
B
loses, gains
C
loses, loses
D
gains, gains
Question 31 Explanation: 
Remember: Oxidation is loss. Reduction is gain.
Question 32
What characteristic of an element determines its specific isotope?

A
Number of protons.
B
Number of neutrons.
C
Number of electrons.
D
Number of quarks.
Question 32 Explanation: 
The number of neutrons is what gives the element its specific isotope. The number of protons determines which element it is, while the number of electrons determines if the atomic particle has a positive, negative, or neutral charge.
Question 33
The addition of a catalyst to a chemical reaction will have what effect?

A
Increase the energy required for the reaction to take place
B
Increase the time required for the reaction to take place
C
Increase the rate at which the reaction takes place
D
Reduce the amount of products in the reaction
Question 33 Explanation: 
A catalyst, by definition, is an enzyme that helps decrease the energy necessary to begin a reaction. Consequently, the addition of a catalyst to a chemical reaction will increase the rate at which the reaction takes place. A reduction in the energy required to begin the reaction means that the reaction will take place more quickly.
Question 34
What is the basic structure of an amino acid?

A
An amine group, a carboxyl group, and a functional R-group.
B
An amine group, a polar side chain, and a non-polar side chain.
C
An amide group, an alcohol group, and a functional R-group.
D
An amine group, and an amide group.
Question 34 Explanation: 
All amino acids share the same basic structure, but vary in the composition of their functional R-group. The amine portion is made up of 1 nitrogen and 3 hydrogen molecules and the carboxyl (or acidic) portion is made up of 1 carbon and 2 oxygen molecules.
Question 35
A concentration of 120.9132 g of MgO in 3 L of solution will be what molality? (The atomic weight are: Magnesium: 24.305 g/mol, Oxygen: 15.9994 g/mol)

A
0.5 mol MgO
B
1.0 mol MgO
C
1.5 mol MgO
D
2.0 mol MgO
Question 35 Explanation: 
Recall that molality is the concentration of a solute in a solution relative to the amount of substance in a specified mass of the solvent. We will begin by calculating the number of moles in the 120.9132 g of MgO- notice that the atomic weights are given in g/mol, meaning that we can find the number of moles by dividing the given amount of MgO by the total atomic weight of MgO:
Hq1
Now divide the number of moles by the number of liters of the solution:
Hq2
Question 36
Polarity is based on the difference in:

A
electronegativity values for the elements involved in the bond.
B
atom number for the elements involved in the bond.
C
concentrations of the elements involved in the bond.
D
quantities of the elements involved in the bond.
Question 36 Explanation: 
Polarity of a bond is based on the differences in electronegativity values for the elements involved in the bond.
Question 37
In a complete combustion reaction involving adequate amounts of oxygen and a compound containing carbon and hydrogen, the products are always?

A
carbon monoxide and oxygen
B
carbon dioxide and water
C
heat and water
D
carbon dioxide and heat
Question 37 Explanation: 
The general chemical formula of a combustion reaction is as follows: CH + O2 → CO2 + H2O. It can be seen that the products are carbon dioxide and water. In combustion reactions, this will always be the case.
Question 38
Between which two molecules is a phosphodiesterase bond?

A
Two sugars
B
Two amino acids
C
Two ammonium molecules
D
PO4 and another molecule
Question 38 Explanation: 
Phosphodiesterase bonds will always be between phosphate and molecules. Sugars have glycosidic linkages and amino acids have peptide bonds.
Question 39
A chemical bond is determined primarily by what particles?

A
Neutrons
B
Protons
C
Quarks
D
Electrons
Question 39 Explanation: 
Recall that an atom consists of a nucleus made up of protons and neutrons bounded together surrounded by electrons. Because these electrons are outside of the nucleus, they are the first particles to experience any force when another atom moves nearby. Another way to deduce that electrons determine a chemical bond is to recall ionic and covalent bonds, which result from the donation and acceptance of electrons and the sharing of electrons, respectively.
Question 40
Which of the following correctly describes the oxidation state of the sulfur atom in sulfuric acid?

A
+5
B
+6
C
+7
D
+8
Question 40 Explanation: 
+6 describes the oxidation state of the sulfur atom in sulfuric acid. The oxidation state of the sulfur atom needs to balance with the oxidation numbers of the hydrogen (+2) and the oxygen (−8).
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