OAT General Chemistry Practice Test 2024 Untimed [Explanation]

Last Updated on June 24, 2024

OAT General Chemistry Practice Test 2024 Untimed [Explanation]. Try our free Optometry Admission Test (OAT) General Chemistry online quiz for better OAT test prep. Biology is integral to mastering the OAT’s Survey of Natural Sciences portion.

While it is not the predominant science in the section, general chemistry does account for 30% of the Survey and is very important to a competitive score. Bolded vocabulary terms are concepts of great importance in the General Chemistry section, but in addition to those terms, there are equations in the text. These equations will be tested on the OAT,

General chemistry is an important subject for the OAT, not only because it is the main focus for an entire subtest but also because a strong general chemistry foundation makes learning organic chemistry, which provides the basis for an entire additional subtest of the Optometry Admission Test.

OAT General Chemistry Practice Test 2024

Test Name	OAT Practice Test 2024
Test Purpose	Admission into optometry schools
Subject	Survey of Natural Sciences
Sub Test	General Chemistry
Sample Questions	30
Time Limit	N/A

Which of the following tends to increase the melting point of a solid?

(A) Increasing molecular weight
(B) Decreasing polarity
(C) Increasing surface area
(D) I and II
(E) I and III
View Answer
Answer: (E) I and III Explanation: Increasing molecular weight and surface area typically lead to higher melting points due to stronger intermolecular forces.

One mole of oxygen gas and two moles of hydrogen are combined in a sealed container at STP. Which of the following statements is true?

(A) The mass of hydrogen gas is greater than the mass of oxygen.
(B) The volume of hydrogen is greater than the volume of oxygen.
(C) The hydrogen and oxygen will react to produce 2 mol of water.
(D) The partial pressure of hydrogen is greater than the partial pressure of oxygen.
(E) The oxygen will react to form hydrogen peroxide.

View Answer

Answer: (D) The partial pressure of hydrogen is greater than the partial pressure of oxygen. Explanation: At STP, the partial pressure of a gas is proportional to its mole fraction in the mixture. Since there are more moles of hydrogen, its partial pressure is greater.

One mole of an ideal gas is compressed to 10 L and heated to 25 °C. What is the pressure of the gas?

(A) 2.4 KPa
(B) 2.4 atm
(C) 0.2 atm
(D) 0.2 KPa
(E) 1 atm

View Answer

Answer: (B) 2.4 atm Explanation: Using the ideal gas law,

P V = n RT

, we can solve for the pressure when given the volume, temperature, and amount of gas.

Which of the following statements is true about the physical properties of liquids and gases?

(A) Liquids and gases are both compressible.
(B) Liquids flow, but gases do not.
(C) Liquids flow, and gases are incompressible.
(D) Liquids flow and gases are compressible.
(E) Gases flow and liquids are incompressible.

View Answer

Answer: (D) Liquids flow and gases are compressible. Explanation: Liquids are incompressible and can flow, while gases are compressible and can also flow.

Silver nitrate (AgNO3) is dissolved in water. One drop of an aqueous solution containing NaCl is added and almost instantly, a white milky precipitate forms. What is the precipitate?

(A) NaCl
(B) NaNO3
(C) AgNO3
(D) AgCl
(E) H2O

View Answer

Answer: (D) AgCl Explanation: When AgNO3 reacts with NaCl, silver chloride (AgCl) precipitates out of the solution as a white solid.

Comparing pure water and a 1 M aqueous solution of NaCl, both at 1 atm of pressure, which of the following statements is most accurate?

(A) The pure water will boil at a higher temperature and be less conductive.
(B) The pure water will boil at a lower temperature and be less conductive.
(C) The pure water will boil at a lower temperature and be more conductive.
(D) The pure water will boil at the same temperature and be more conductive.
(E) The pure water will freeze at a higher temperature and be less conductive.

View Answer

Answer: (B) The pure water will boil at a lower temperature and be less conductive. Explanation: The presence of NaCl in the solution raises the boiling point and increases conductivity due to the ions present.

50 grams of acetic acid (C2H4O2) are dissolved in 200 g of water. Calculate the weight % and mole fraction of the acetic acid in the solution.

(A) 20%, 0.069
(B) 0.069%, 0.20
(C) 25%, 0.075
(D) 20%, 0.075
(E) 15%, 0.050

View Answer

Answer: (D) 20%, 0.075 Explanation: Weight percent is calculated as (mass of solute / total mass of solution) × 100. Mole fraction is the ratio of solute moles to the solution’s total moles.

One liter of a 0.02 M solution of methanol in water is prepared. What is the mass of methanol in the solution, and what is the approximate molality of methanol?

(A) 0.64 g, 0.02 m
(B) 0.32 g, 0.01 m
(C) 0.64 g, 0.03 m
(D) 0.32 g, 0.02 m
(E) 0.16 g, 0.01 m

View Answer

Answer: (A) 0.64 g, 0.02 m Explanation: Molarity is moles per liter. The mass of methanol is found by multiplying the molarity by the molar mass of methanol. Molality is moles of solute per kg of solvent.

A material has a half-life of 2 years. If you started with 1 kg of the material, how much would be left after 8 years?

(A) 1 kg
(B) 0.5 kg
(C) 0.06 kg
(D) 0.12 kg
(E) 0.25 kg

View Answer

Answer: (D) 0.12 kg Explanation: After each half-life, half of the remaining material decays. After 8 years (4 half-lives), the remaining mass is (1/2)^4 × 1 kg = 0.0625 kg ≈ 0.12 kg.

Which of the following statements about radioactive decay is true?

(A) The sum of the mass of the daughter particles is less than that of the parent nucleus.
(B) The sum of the mass of the daughter particles is greater than that of the parent nucleus.
(C) The sum of the mass of the daughter particles is equal to that of the parent nucleus.
(D) The sum of the mass of the daughter particles cannot be accurately measured.
(E) Radioactive decay increases the atomic number.

View Answer

Answer: (A) The sum of the mass of the daughter particles is less than that of the parent nucleus. Explanation: Due to the release of energy and particles, the total mass of the decay products is slightly less than the original mass of the parent nucleus.

Hund’s rule regarding electronic configuration states:

(A) Electrons in the same orbital must have opposite spins.
(B) Electrons must fill lower energy orbitals before filling higher energy orbitals.
(C) Electrons must populate empty orbitals of equal energy before filling occupied orbitals.
(D) Electrons must have the same nuclear spin as the nucleus.
(E) Electrons must pair up in orbitals before moving to the next orbital.

View Answer

Answer: (C) Electrons must populate empty orbitals of equal energy before filling occupied orbitals. Explanation: Hund’s rule states that electrons will fill empty orbitals of the same energy before pairing up in the same orbital.

Arrange the following compounds from most polar to least polar: F2, CH3CH2Cl, NaCl, CH3OH.

(A) NaCl > CH3OH > CH3CH2Cl > F2
(B) F2 > NaCl > CH3OH > CH3CH2Cl
(C) CH3OH > NaCl > F2 > CH3CH2Cl
(D) NaCl > F2 > CH3OH > CH3CH2Cl
(E) CH3CH2Cl > NaCl > F2 > CH3OH

View Answer

Answer: (A) NaCl > CH3OH > CH3CH2Cl > F2 Explanation: NaCl is an ionic compound and the most polar. CH3OH has hydrogen bonding, making it the next most polar. CH3CH2Cl has dipole-dipole interactions, and F2 is nonpolar.

What is the chemical composition of ammonium sulfate?

(A) N 21%, H 3%, S 24%, O 32%
(B) N 10%, H 6%, S 24%, O 60%
(C) N 10%, H 4%, S 12%, O 74%
(D) N 21%, H 6%, S 24%, O 48%
(E) N 18%, H 6%, S 32%, O 44%

View Answer

Answer: (A) N 21%, H 3%, S 24%, O 32% Explanation: The molar masses of N, H, S, and O in (NH4)2SO4 are used to calculate their percentage composition.

Calculate the mass of water produced from the reaction of 1 kg of n-heptane with oxygen. n-heptane (1 kg) + 11 O2 → 7 CO2 + 8 H2O

(A) 144 g
(B) 8 kg
(C) 800 g
(D) 1.4 kg
(E) 720 g

View Answer

Answer: (D) 1.4 kg Explanation: The balanced equation shows the stoichiometry of the reaction. 1 kg of n-heptane produces 8 moles of water, which translates to 1.4 kg.

The following equation can describe the overall reaction A→D: What would be the rate law for the overall reaction of A to D?

(A) Rate = k[D]/[A]
(B) Rate = k[B]
(C) Rate = [B]
(D) Rate = k[C]/[B]
(E) Rate = k[A]

View Answer

Answer: (E) Rate = k[A] Explanation: The rate law depends on the slowest step in the reaction mechanism and typically involves the concentration of the reactant in that step.

Which of the following are considered Lewis acids?

(A) H2SO4

(B) AlCl3

(D) FeCl3

(E) HNO3

(A) II and IV
(B) II and III
(C) I and IV
(D) I and II
(E) III and IV

View Answer

Answer: (A) II and IV Explanation: Lewis acids are electron pair acceptors. AlCl3 and FeCl3 can accept electron pairs and are thus considered Lewis acids.

What is the pH of a buffer containing 0.2 M NaOAc and 0.1 M AcOH? The pKa of acetic acid is 4.75.

(A) 4
(B) 5
(C) 6
(D) 7
(E) 3

View Answer

Answer: (B) 5 Explanation: Using the Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), we find that the pH of the buffer is 5.

100 g of NH3 are cooled from 100 °C to 25 °C. What is the heat change for this transition? The heat capacity of ammonia gas is 35.1 J/(mol·K).

(A) -263 KJ
(B) 15.5 KJ
(C) -15.5 KJ
(D) 263 KJ
(E) -150 KJ

View Answer

Answer: (A) -263 KJ Explanation: The heat change (q) can be calculated using q = mcΔT. Here, the mass and heat capacity are used to find the total heat change.

Which of the following molecules are alkenes?

(A) I
(B) II
(C) III
(D) IV
(E) V

View Answer

Answer: (A) I Explanation: Alkenes are hydrocarbons with at least one carbon-carbon double bond (C=C). The molecular structure must show this feature.

Methyl mercury is a toxin produced indirectly from what energy source?

(A) Oil
(B) Natural gas
(C) Wood
(D) Coal
(E) Nuclear power

View Answer

Answer: (D) Coal Explanation: Methyl mercury is often produced as a byproduct of burning coal, which releases mercury into the environment, where bacteria can convert it into methyl mercury.

A liquid is heated from 50 °C to 80 °C. Which of the following statements is generally true about the solubility of solids and gases in the liquid?

(A) The solubility of solids will increase and the solubility of gases will decrease.
(B) The solubility of solids will decrease and the solubility of gases will increase.
(C) The solubility of solids will increase and the solubility of gases will increase.
(D) The solubility of solids will decrease and the solubility of gases will decrease.
(E) The solubility of solids and gases remains unchanged.

View Answer

Answer: (A) The solubility of solids will increase and the solubility of gases will decrease. Explanation: Generally, the solubility of solids increases with temperature, while the solubility of gases decreases.

Adding a catalyst to a reaction will do which of the following to that reaction:

(A) Shift the reaction equilibrium towards the products.
(B) Increase the temperature of the reaction.
(C) Decrease the energy of activation for the reaction.
(D) Increase the purity of the reaction products.
(E) Decrease the enthalpy change of the reaction.

View Answer

Answer: (C) Decrease the energy of activation for the reaction. Explanation: Catalysts lower the activation energy required for a reaction to proceed, thereby increasing the reaction rate.

Place the following in the correct order of increasing acidity: H3PO4, HF, HCl, H2O, NH3.

(A) H3PO4 < H2O < NH3 < HF < HCl
(B) NH3 < H2O < HF < H3PO4 < HCl
(C) H2O < NH3 < HF < H3PO4 < HCl
(D) NH3 < H2O < HF < HCl < H3PO4
(E) H3PO4 < HCl < HF < NH3 < H2O

View Answer

Answer: (B) NH3 < H2O < HF < H3PO4 < HCl Explanation: Acidity increases with increasing ability to donate protons. HCl is a strong acid, HF is a weak acid, H3PO4 is moderately strong, H2O is very weakly acidic, and NH3 is basic.

To make an excellent buffering system in the pH range of 5-9, which acid/base combinations would likely work the best?

(A) HCl/NaOH
(B) HNO3/NaNO3
(C) H2SO4/NaHSO4
(D) NaH2PO4/Na2HPO4
(E) NH3/NH4Cl

View Answer

Answer: (D) NaH2PO4/Na2HPO4 Explanation: A buffering system works best when the pKa of the acid is close to the desired pH range. The phosphate buffer system is effective in the pH range of 5-9.

Determine the heat of combustion for the following reaction: Propane + 5 O2 → 3 CO2 + 4 H2O. The standard heats of formation for propane, CO2 and water are -103.8 kJ/mol, -393.5 kJ/mol, and -285.8 kJ/mol respectively.

(A) -2220 kJ/mol
(B) -2323.7 kJ/mol
(C) 2220 kJ/mol
(D) 2323.7 kJ/mol
(E) -1500 kJ/mol

View Answer

Answer: (B) -2323.7 kJ/mol Explanation: The heat of combustion can be calculated using the heats of formation of the reactants and products in the reaction.

reactants)\Delta H = \sum (\Delta H_f \text{ of products}) – \sum (\Delta H_f \text{ of reactants})

A 1 kg block each of iron, lead, and nickel are heated from 20 °C to 30 °C. Which of the following statements about the blocks is true?

(A) The lead will heat faster than the iron and the nickel.
(B) The iron required more heat to reach 30 °C than the nickel or lead.
(C) All three blocks required a different amount of heat to reach 30 °C.
(D) The iron required more time to reach 30 °C.
(E) The nickel required less heat to reach 30 °C.

View Answer

Answer: (C) All three blocks required a different amount of heat to reach 30 °C. Explanation: The specific heat capacities of iron, lead, and nickel differ, so the amount of heat required to change their temperatures varies.

In the reaction Pb + H2SO4 + H2O → PbSO4 + H2 + H2O, which element is oxidized and reduced?

(A) Lead is reduced and hydrogen is oxidized.
(B) Lead is oxidized and hydrogen is oxidized.
(C) Lead is reduced and sulfate is oxidized.
(D) Lead is oxidized and hydrogen is reduced.
(E) Hydrogen is reduced and oxygen is oxidized.

View Answer

Answer: (D) Lead is oxidized and hydrogen is reduced. Explanation: In the reaction, lead (Pb) is oxidized from 0 to +2 oxidation state, and hydrogen (H) is reduced from +1 to 0 oxidation state.

Which of the following elements would likely be good reducing agents?

(A) Br2
(B) N2
(C) Na
(D) Ne
(E) O2

View Answer

Answer: (C) Na Explanation: Sodium (Na) is a good reducing agent because it easily loses an electron to form a Na+ ion, thereby reducing other substances.

Molten magnesium chloride is electrolyzed. The products formed from this reaction are:

(A) Mg(0) at the anode and Cl- at the cathode
(B) Mg2+ at the anode and Cl- at the cathode
(C) Mg(0) at the cathode and Cl2 at the anode
(D) Mg(0) at the anode and Cl2 at the cathode
(E) Mg2+ at the cathode and Cl2 at the anode

View Answer

Answer: (C) Mg(0) at the cathode and Cl2 at the anode. Explanation: During the electrolysis of MgCl2, magnesium ions are reduced to Mg metal at the cathode, and chloride ions are oxidized to Cl2 gas at the anode.

The general formula for an alkane is:

(A) CnH2n
(B) CnH2n+2
(C) C2nH2n+2
(D) (CH2)n
(E) CnHn

View Answer

Answer: (B) CnH2n+2 Explanation: Alkanes are saturated hydrocarbons with the general formula CnH2n+2, indicating that each carbon atom forms four single bonds.

See also:

OAT Practice Test 2024 With Study Guide (Free PDF)

Untimed Tests with Explanation