HESI A2
HESI A2 Chemistry Practice Questions
1. 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.
2. What are bases or alkaline solutions known as?
- A. Hydrogen acceptors
- B. Solutions of low pH
- C. Hydrogen donors
- D. Amphoteric
Correct answer: A
Rationale: Bases or alkaline solutions are known as 'hydrogen acceptors.' They accept protons (H+) in chemical reactions, as opposed to acids that donate protons. This property allows bases to neutralize acids and form salts. Choice B, 'Solutions of low pH,' is incorrect because bases have high pH values, not low. Choice C, 'Hydrogen donors,' is incorrect as bases do not donate protons but accept them. Choice D, 'Amphoteric,' refers to substances that can act as both acids and bases, which is not the definition of bases. Therefore, the correct answer is A.
3. Which element is a metalloid?
- A. Silicon
- B. Lead
- C. Helium
- D. Aluminum
Correct answer: A
Rationale: The correct answer is 'Silicon.' Silicon is a metalloid, which means it has properties of both metals and nonmetals. It is commonly used in electronic devices due to its semiconductor properties. Lead (Choice B) is a metal, Helium (Choice C) is a noble gas, and Aluminum (Choice D) is a metal.
4. What is the correct formula for potassium chloride?
- A. NaCl
- B. KCl
- C. KCl
- D. ClK
Correct answer: B
Rationale: The correct formula for potassium chloride is KCl. In chemical formulas, the symbol for the cation (positive ion) comes first followed by the symbol for the anion (negative ion). Potassium is represented by the symbol K, while chloride is represented by the symbol Cl. Therefore, the formula for potassium chloride is KCl. Choice A (NaCl) is the formula for sodium chloride, not potassium chloride. Choice C is a duplicate of choice B, and choice D (ClK) is an incorrect arrangement of the symbols for potassium and chloride.
5. What charge do Group IIIA elements have?
- A. +1
- B. +2
- C. +3
- D. 0
Correct answer: C
Rationale: Group IIIA elements, also known as Group 13 elements, have a common oxidation state of +3. This is because they have three valence electrons and tend to lose these electrons to achieve a stable electron configuration, resulting in a +3 charge. Choice A (+1) and Choice B (+2) are incorrect because Group IIIA elements typically lose all three valence electrons to attain a stable configuration, leading to a +3 charge. Choice D (0) is incorrect as these elements do not gain electrons but rather lose them, resulting in a positive charge.
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