AAMC CHEM questions and answers
with solutions 2025
Which of the following compounds has the same geometry as methane?
A.) H2S
B.) CO2
C.) XeF4
D.) SiCl4 - ANSWER D.) SiCl4
Methane (CH4) consists of a group IV element (C) involved in four identical bonds, with no lone electron
pairs. It is therefore tetrahedral. SiCl4 likewise consists of a group IV element (Si) involved in four
identical bonds. While the sulfur in H2S is also surrounded by four electron pairs which are directed at
the corners of a tetrahedron, it is important to note that the geometry or shape of a molecule refers only
to the positions of atoms, not electron pairs. H2S has a bent shape. In CO2, carbon is bonded to only two
atoms, with no lone pairs, so the molecule is linear. Lastly, in XeF4, the xenon is surrounded by the four
fluorine atoms with lone pairs above and below, giving a square planar appearance. Therefore answer
choice D is the correct response.
Creating a lower pressure inside the distilling apparatus will _________ the boiling points of both liquids
and _______ their difference in boiling point, - ANSWER lower; narrow
If a leak develops in the vacuum distillation apparatus, the boiling points of the two components of
caraway seed oil will:
A. both increase.
B. both decrease.
C. both remain the same.
D. become more similar. - ANSWER A. both increase.
The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the
surface pressure. The normal boiling point is measured at 1 atm pressure. The vapor pressure of a liquid
increases with increasing temperature. Hence, the boiling point of a liquid decreases as the pressure on
,the surface of the liquid is decreased. If a leak develops in the apparatus, the surface pressure will
increase, as will the boiling points of both liquids. Thus, answer choice A is the best answer.
How many sodium ions are in the initial 50.00-mL solution of Na2CO3? (7.15 g of Na2CO3•10H2O (molar
mass 286.14)
A. 1.50 × 1022
B. 3.00 × 1022
C. 6.02 × 1023
D. 12.0 × 1023 - ANSWER B. 3.00 × 1022
The solution contains 7.15 g Na2CO3×10H2O. Dividing by the molar mass will give the number of moles:
(7.15 g)/(286.14 g/mol) = 0.0250 mol. Because each mole of Na2CO3×10H2O contains 2 mol Na+, there
is 0.0500 mol Na+. Using Avogadro's number, the number of sodium ions is (0.0500 mol)(6.02 × 1023
ions/mol) = 3.01 × 1022 ions. Thus, B is the best answer.
Red litmus paper - ANSWER Stays red for acids, turns blue for bases
If red litmus paper is dipped into the Na2CO3 solution, it will:
A. remain red, because carbonate is an acidic salt.
B. remain red, because sodium carbonate is neutral.
C. turn blue, because carbonate reacts with water to produce OH-.
D. turn blue, because sodium ions form sodium hydroxide in water. - ANSWER C. turn blue, because
carbonate reacts with water to produce OH-.
In water, carbonate will undergo the following reaction: CO32-(aq) + H2O(l) → HCO3-(aq) + OH-(aq). Red
litmus paper will turn blue in a base. Thus, C is the best answer.
According to the information in the passage, the gas that evolves is: (To one portion is added an excess
of 6 M HCl, which results in the disappearance of the precipitate and a rapid evolution of a gas)
NiSO4•6H2O & Na2CO3•10H2O mixture.
, A. sulfur dioxide.
B. sulfur trioxide.
C. carbon dioxide.
D. carbon monoxide. - ANSWER According to the passage, the gas is given off when HCl is added to one
portion of the slurry. HCl reacts with CO3^(2-) to form CO2(g). Thus, C is the best answer.
The ion responsible for the color of the solutions is:
A. sulfate, because sulfur has s and p orbitals.
B. nickel(II), because it has a charge of +2.
C. nickel(II), because it has unfilled d orbitals.
D. sulfate, because it is a resonance-stabilized anion. - ANSWER C. nickel(II), because it has unfilled d
orbitals.
The solution containing nickel(II) ions is green-colored. The color arises because nickel(II) ion has partially
filled d orbitals and the electrons in the lower energy d orbitals absorb visible light to move to the higher
energy d orbitals. Thus, C is the best answer.
What mass of CDP (403 g mol−1) is in 10 mL of the buffered solution at the beginning of Experiment 1?
(The chemist dissolves 16 mmol CDP in 1 L of an aqueous solution)
A.) 6.4 × 10−4 g
B.) 6.4 × 10−3 g
C.) 6.4 × 10−2 g
D.) 6.4 × 10−1 g - ANSWER C.) 6.4 × 10−2 g
The solution in Experiment 1 was formed by dissolving 16 mmol of CDP in 1 L of buffer. Thus, the
solution is 16 mM in the diphosphate CDP. Since each mole of CDP weighs 403 g, then 16 mmol (or 16 ×
10−3 mol) weighs
with solutions 2025
Which of the following compounds has the same geometry as methane?
A.) H2S
B.) CO2
C.) XeF4
D.) SiCl4 - ANSWER D.) SiCl4
Methane (CH4) consists of a group IV element (C) involved in four identical bonds, with no lone electron
pairs. It is therefore tetrahedral. SiCl4 likewise consists of a group IV element (Si) involved in four
identical bonds. While the sulfur in H2S is also surrounded by four electron pairs which are directed at
the corners of a tetrahedron, it is important to note that the geometry or shape of a molecule refers only
to the positions of atoms, not electron pairs. H2S has a bent shape. In CO2, carbon is bonded to only two
atoms, with no lone pairs, so the molecule is linear. Lastly, in XeF4, the xenon is surrounded by the four
fluorine atoms with lone pairs above and below, giving a square planar appearance. Therefore answer
choice D is the correct response.
Creating a lower pressure inside the distilling apparatus will _________ the boiling points of both liquids
and _______ their difference in boiling point, - ANSWER lower; narrow
If a leak develops in the vacuum distillation apparatus, the boiling points of the two components of
caraway seed oil will:
A. both increase.
B. both decrease.
C. both remain the same.
D. become more similar. - ANSWER A. both increase.
The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the
surface pressure. The normal boiling point is measured at 1 atm pressure. The vapor pressure of a liquid
increases with increasing temperature. Hence, the boiling point of a liquid decreases as the pressure on
,the surface of the liquid is decreased. If a leak develops in the apparatus, the surface pressure will
increase, as will the boiling points of both liquids. Thus, answer choice A is the best answer.
How many sodium ions are in the initial 50.00-mL solution of Na2CO3? (7.15 g of Na2CO3•10H2O (molar
mass 286.14)
A. 1.50 × 1022
B. 3.00 × 1022
C. 6.02 × 1023
D. 12.0 × 1023 - ANSWER B. 3.00 × 1022
The solution contains 7.15 g Na2CO3×10H2O. Dividing by the molar mass will give the number of moles:
(7.15 g)/(286.14 g/mol) = 0.0250 mol. Because each mole of Na2CO3×10H2O contains 2 mol Na+, there
is 0.0500 mol Na+. Using Avogadro's number, the number of sodium ions is (0.0500 mol)(6.02 × 1023
ions/mol) = 3.01 × 1022 ions. Thus, B is the best answer.
Red litmus paper - ANSWER Stays red for acids, turns blue for bases
If red litmus paper is dipped into the Na2CO3 solution, it will:
A. remain red, because carbonate is an acidic salt.
B. remain red, because sodium carbonate is neutral.
C. turn blue, because carbonate reacts with water to produce OH-.
D. turn blue, because sodium ions form sodium hydroxide in water. - ANSWER C. turn blue, because
carbonate reacts with water to produce OH-.
In water, carbonate will undergo the following reaction: CO32-(aq) + H2O(l) → HCO3-(aq) + OH-(aq). Red
litmus paper will turn blue in a base. Thus, C is the best answer.
According to the information in the passage, the gas that evolves is: (To one portion is added an excess
of 6 M HCl, which results in the disappearance of the precipitate and a rapid evolution of a gas)
NiSO4•6H2O & Na2CO3•10H2O mixture.
, A. sulfur dioxide.
B. sulfur trioxide.
C. carbon dioxide.
D. carbon monoxide. - ANSWER According to the passage, the gas is given off when HCl is added to one
portion of the slurry. HCl reacts with CO3^(2-) to form CO2(g). Thus, C is the best answer.
The ion responsible for the color of the solutions is:
A. sulfate, because sulfur has s and p orbitals.
B. nickel(II), because it has a charge of +2.
C. nickel(II), because it has unfilled d orbitals.
D. sulfate, because it is a resonance-stabilized anion. - ANSWER C. nickel(II), because it has unfilled d
orbitals.
The solution containing nickel(II) ions is green-colored. The color arises because nickel(II) ion has partially
filled d orbitals and the electrons in the lower energy d orbitals absorb visible light to move to the higher
energy d orbitals. Thus, C is the best answer.
What mass of CDP (403 g mol−1) is in 10 mL of the buffered solution at the beginning of Experiment 1?
(The chemist dissolves 16 mmol CDP in 1 L of an aqueous solution)
A.) 6.4 × 10−4 g
B.) 6.4 × 10−3 g
C.) 6.4 × 10−2 g
D.) 6.4 × 10−1 g - ANSWER C.) 6.4 × 10−2 g
The solution in Experiment 1 was formed by dissolving 16 mmol of CDP in 1 L of buffer. Thus, the
solution is 16 mM in the diphosphate CDP. Since each mole of CDP weighs 403 g, then 16 mmol (or 16 ×
10−3 mol) weighs
