HESI A2
HESI A2 Chemistry Practice Questions
1. Which of these represents a strong acid?
- A. CH₃COOH
- B. H₂SO₄
- C. NH₃
- D. KOH
Correct answer: B
Rationale: Among the options provided, H₂SO₄ (sulfuric acid) represents a strong acid. Strong acids completely ionize in water to produce a high concentration of H+ ions. Sulfuric acid is a strong acid known for its ability to dissociate almost completely in water, making it a strong acid. Choice A, CH₃COOH (acetic acid), is a weak acid that only partially dissociates in water. Choices C and D, NH₃ (ammonia) and KOH (potassium hydroxide), are bases and not acids.
2. Which substance is a product of photosynthesis?
- A. Carbon dioxide
- B. Oxygen
- C. Water
- D. Glucose
Correct answer: D
Rationale: During photosynthesis, plants and other organisms convert carbon dioxide and water into glucose and oxygen. Glucose is a carbohydrate produced by plants as a result of photosynthesis, serving as their main source of energy. Oxygen is released as a byproduct of this process, while carbon dioxide and water are the raw materials used to produce glucose. Therefore, the correct answer is 'Glucose,' making it a vital product of the photosynthesis process. Choices A, B, and C are incorrect as carbon dioxide and water are the reactants needed for photosynthesis, and oxygen is released as a byproduct.
3. To the nearest whole number, what is the mass of one mole of hydrogen iodide?
- A. 2 g/mol
- B. 58 g/mol
- C. 87 g/mol
- D. 128 g/mol
Correct answer: C
Rationale: The molar mass of hydrogen iodide (HI) is the sum of the atomic masses of its constituent elements. Hydrogen (H) has a molar mass of approximately 1 g/mol, and iodine (I) has a molar mass of about 127 g/mol. Thus, the molar mass of hydrogen iodide (HI) is approximately 1 + 127 = 128 g/mol. Rounding to the nearest whole number, the molar mass of hydrogen iodide is 128 g/mol, which is closest to choice C. Choice A (2 g/mol) is too low and does not reflect the correct molar mass of hydrogen iodide. Choice B (58 g/mol) is significantly lower than the actual molar mass. Choice D (128 g/mol) matches the calculated molar mass but is not the nearest whole number as requested.
4. What is the correct name of AgNO₃?
- A. Argent nitrous
- B. Argent oxide
- C. Silver nitrite
- D. Silver nitrate
Correct answer: D
Rationale: The correct name for AgNO₃ is silver nitrate. In chemical nomenclature, the element symbol Ag represents silver, and the polyatomic ion NO₃ is known as nitrate. Therefore, when the silver ion (Ag⁺) combines with the nitrate ion (NO₃⁻), the resulting compound is named silver nitrate (AgNO₃). Choices A, B, and C are incorrect because they do not accurately represent the composition of AgNO₃. Argent nitrous (Choice A) and Argent oxide (Choice B) do not reflect the correct anion, and Silver nitrite (Choice C) uses a different anion altogether.
5. What is the energy required to remove the outermost electron from an atom called?
- A. covalent bonding
- B. electronegativity
- C. atomic radius
- D. ionization energy
Correct answer: D
Rationale: Ionization energy is the energy needed to remove the outermost electron from an atom, resulting in the formation of a positively charged ion. The higher the ionization energy, the more difficult it is to extract an electron. Electronegativity, however, measures an atom's ability to attract shared electrons in a chemical bond. Atomic radius refers to the distance from the nucleus to the outermost electron. Covalent bonding involves sharing electron pairs between atoms to create a stable bond. Therefore, the correct answer is ionization energy as it specifically relates to the energy needed to remove an electron from an atom.
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