HESI A2
Chemistry HESI A2 Practice Test
1. Which of the following pH values is most likely for lemon juice?
- A. 3
- B. 5
- C. 7
- D. 9
Correct answer: A
Rationale: Lemon juice is highly acidic with a pH around 2-3, making it more acidic than neutral substances. A pH of 5 is too high for lemon juice, indicating less acidity. Similarly, pH 7 is neutral, and pH 9 would be alkaline, which is not characteristic of lemon juice. Therefore, the correct answer is option A (pH 3).
2. Which is a property of an ionic compound?
- A. Low melting point
- B. Poor conductivity
- C. Shared electrons
- D. Crystalline shape
Correct answer: D
Rationale: Ionic compounds are composed of positively and negatively charged ions that are held together by strong electrostatic forces. These ions arrange themselves in a repeating pattern to form a stable and orderly structure known as a crystalline shape. This is a characteristic property of ionic compounds, making choice D the correct answer. Choices A, B, and C are incorrect because ionic compounds typically have high melting points, good conductivity in the molten or dissolved state, and do not involve shared electrons but rather the transfer of electrons between atoms.
3. What is the oxidation state of the chlorine atom in the compound HCl?
- A. +1
- B. -1
- C. +2
- D. -2
Correct answer: B
Rationale: In the compound HCl (hydrochloric acid), the hydrogen atom has an oxidation state of +1 based on the rules of assigning oxidation states. Since the overall compound is neutral, the oxidation state of chlorine must be -1 to balance the charge. Chlorine typically has an oxidation state of -1 in binary compounds with nonmetals, such as HCl. Therefore, the correct answer is -1. Choices A, C, and D are incorrect as the oxidation state of chlorine in HCl is -1, not +1, +2, or -2.
4. Which of the following is not an allotrope of carbon?
- A. Diamond
- B. Graphite
- C. Fluorine
- D. Buckminsterfullerene
Correct answer: C
Rationale: The correct answer is C: Fluorine. Allotropes of carbon are different forms of the same element. Diamonds, graphite, and buckminsterfullerene are all allotropes of carbon. However, fluorine is a separate chemical element and not an allotrope of carbon. Therefore, fluorine does not belong to the group of carbon allotropes.
5. How many neutrons are in an atom of uranium-235?
- A. 92
- B. 125
- C. 143
- D. 235
Correct answer: A
Rationale: The correct answer is A: '92'. To determine the number of neutrons in an atom, you subtract the atomic number (number of protons) from the atomic mass number. For uranium-235, the atomic number is 92, and the atomic mass number is 235. Subtracting 92 from 235 gives us 143 neutrons in an atom of uranium-235. Therefore, options B, C, and D are incorrect as they do not represent the correct number of neutrons in an atom of uranium-235.
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