Nokea
What is the coefficient of O after the following equation is balanced?
- A. 1
- B. 2
- C. 3
- D. 4
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.
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What is the charge of an alpha particle?
- A. -1
- B. +1
- C. +2
- D. No charge
Correct Answer: C
Rationale: An alpha particle consists of two protons and two neutrons, resulting in a total charge of +2 due to the presence of two positively charged protons. Therefore, the correct answer is C, indicating a charge of +2. Choices A, B, and D are incorrect because an alpha particle is positively charged due to the two protons it contains, resulting in a charge of +2.
What is the pH of acids?
- A. 7.5
- B. < 7
- C. > 7
- D. 7
Correct Answer: B
Rationale: The correct answer is B: < 7. Acids have a pH lower than 7, indicating higher acidity. A pH below 7 signifies an acidic solution, with lower values indicating stronger acids. Choice A (7.5) is incorrect as it is greater than 7, which is alkaline. Choice C (> 7) is incorrect as values greater than 7 represent alkaline/basic solutions. Choice D (7) is incorrect because a pH of 7 is neutral, not acidic.
Carbon-12 and carbon-14 are isotopes. What do they have in common?
- A. Number of nuclear particles
- B. Number of protons
- C. Number of neutrons
- D. Mass number
Correct Answer: C
Rationale: Isotopes are atoms of the same element with the same number of protons (which determines the element) but different numbers of neutrons. Both carbon-12 and carbon-14 have 6 protons (hence they are both carbon atoms) but different numbers of neutrons: carbon-12 has 6 neutrons, while carbon-14 has 8 neutrons. Therefore, the correct answer is the number of neutrons. Choices A, B, and D are incorrect because isotopes may have different numbers of nuclear particles (protons + neutrons), protons, and mass numbers, respectively.
Al(NO3)3 + H2SO4 → Al2(SO4)3 + HNO3 is an example of which kind of reaction?
- A. Decomposition reaction
- B. Synthesis reaction
- C. Single replacement reaction
- D. Double replacement reaction
Correct Answer: C
Rationale: The given chemical equation represents a single replacement reaction. In this reaction, aluminum (Al) displaces hydrogen in sulfuric acid (H2SO4), forming aluminum sulfate (Al2(SO4)3) and releasing nitric acid (HNO3). Single replacement reactions involve an element replacing another element in a compound, which is evident in this reaction. Choice A, Decomposition reaction, is incorrect because decomposition reactions involve a single compound breaking down into two or more substances. Choice B, Synthesis reaction, is incorrect as it involves the combination of two or more substances to form a more complex compound. Choice D, Double replacement reaction, is also incorrect as it involves an exchange of ions between two compounds to form two new compounds.
What is the normal body temperature in Fahrenheit?
- A. 96°F
- B. 98.6°F
- C. 100°F
- D. 95°F
Correct Answer: B
Rationale: The normal body temperature for humans is 98.6°F, which is equivalent to 37°C. This temperature is considered the average baseline for most individuals when measured orally. Choice A (96°F) is too low for normal body temperature. Choice C (100°F) is too high for normal body temperature. Choice D (95°F) is also lower than the normal body temperature range. Therefore, the correct answer is B, 98.6°F.