what is the coefficient of o after the following equation is balanced
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HESI A2

Chemistry HESI A2 Practice Test

1. What is the coefficient of O after the following equation is balanced?

Correct answer: A

Rationale: In a balanced chemical equation, the coefficient of oxygen (O) in O2 is already 2, so there is no need to adjust its coefficient further. Therefore, the coefficient of O remains as 1. Since the coefficient of O2 is 2, each O atom is represented by the coefficient of 1, and it does not change during the balancing process. Choices B, C, and D are incorrect as they suggest changing the coefficient of oxygen, which is not necessary for O2 in a balanced equation.

2. When a dielectric material is inserted between the plates of a charged capacitor, what will happen to the capacitance?

Correct answer: A

Rationale: When a dielectric material is inserted between the plates of a charged capacitor, the capacitance will increase. This is because the presence of a dielectric material reduces the electric field between the plates, allowing more charge to be stored for a given voltage, thus increasing the capacitance. Choice B is incorrect because adding a dielectric material increases capacitance. Choice C is incorrect because capacitance changes when a dielectric is added. Choice D is incorrect because the effect of a dielectric on capacitance is predictable.

3. John F. Kennedy was a senator before he _______ president in 1960.

Correct answer: C

Rationale: The correct answer is 'Was elected' as it is the passive voice construction needed in this context. The sentence is referring to an action that happened to John F. Kennedy (being elected president), so the passive voice 'was elected' is the appropriate form to use in this sentence. Choice A, 'Elected,' is incorrect because it is the active voice and does not fit the sentence structure. Choice B, 'Was electing,' is incorrect as it is the continuous form of the verb, which is not suitable in this sentence. Choice D, 'Had elected,' is incorrect because it implies a past perfect tense which is not required in this context.

4. A paroxysm is a sudden spasm. Another word for this might be ___________.

Correct answer: A

Rationale: The correct answer is A: "convulsion." A paroxysm is defined as a sudden spasm or convulsion. The word "convulsion" specifically refers to a violent and involuntary contraction or spasm of muscles, which aligns perfectly with the description of a paroxysm. On the other hand, choices B, C, and D are incorrect. "Symptom" (B) refers to a manifestation of a condition rather than a physical spasm. "Efficacy" (C) relates to effectiveness or success, not a sudden spasm. "Embolism" (D) refers to the obstruction of a blood vessel, which is unrelated to the concept of a sudden spasm. Therefore, convulsion is the most suitable synonym for a paroxysm in this context.

5. Which type of chemical reaction involves an active metal reacting with an ionic compound to create a new compound?

Correct answer: B

Rationale: The correct answer is 'Single replacement.' In a single replacement reaction, an active metal replaces another element in an ionic compound, resulting in the formation of a new compound. Option A, 'Combustion,' involves a substance rapidly reacting with oxygen to release energy in the form of heat and light. Option C, 'Synthesis,' involves the combination of two or more substances to form a more complex product. Option D, 'Decomposition,' involves the breakdown of a compound into simpler substances.

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