Nokea
Which compound is a Hydrogen or proton donor, corrosive to metals, causes blue litmus paper to become red, and becomes less acidic when mixed with a base?
- A. Base
- B. Acid
- C. Salt
- D. Hydroxide
Correct Answer: B
Rationale: The correct answer is 'Acid.' An acid is a compound that donates protons (H+), is corrosive to metals, and turns blue litmus paper red. When an acid is mixed with a base, they react to form salts and water, resulting in a decrease in acidity. Choices A, C, and D are incorrect because bases accept protons rather than donate them, salts are the products of acid-base reactions, and hydroxides are typically bases, not acids.
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Among the following elements, which is a nonmetal?
- A. Mercury
- B. Magnesium
- C. Sulfur
- D. Potassium
Correct Answer: C
Rationale: Sulfur is a nonmetal as it is located on the right side of the periodic table. Nonmetals generally exhibit properties such as being brittle, poor conductors of heat and electricity, and having lower melting points compared to metals. Mercury (A), Magnesium (B), and Potassium (D) are all metals due to their metallic properties. Mercury is a liquid metal at room temperature, Magnesium is a solid metal, and Potassium is a solid metal as well. Therefore, the correct answer is C, Sulfur.
What is the boiling point of water in °C?
- A. 90°C
- B. 100°C
- C. 95°C
- D. 80°C
Correct Answer: B
Rationale: The correct answer is 100°C. The boiling point of water in Celsius is 100°C, which is standard at sea level. This is the temperature at which water changes from a liquid to a gas phase under standard atmospheric pressure. Choice A (90°C), Choice C (95°C), and Choice D (80°C) are incorrect because they do not represent the standard boiling point of water at sea level.
What is 0 K equal to in °C?
- A. -300°C
- B. -273°C
- C. -250°C
- D. -200°C
Correct Answer: B
Rationale: 0 Kelvin, also known as absolute zero, is equal to -273°C. This is the point at which all molecular motion stops, making it the lowest possible temperature on the Kelvin scale. Choice A (-300°C) is incorrect as it is not the correct conversion of 0 K to °C. Choice C (-250°C) and Choice D (-200°C) are also incorrect as they do not correspond to the accurate conversion of 0 K to °C.
What is the correct name of ZnSOâ‚„?
- A. Zinc sulfate
- B. Zinc sulfide
- C. Zinc sulfur
- D. Zinc oxide
Correct Answer: A
Rationale: The correct name of ZnSOâ‚„ is zinc sulfate. In this compound, zinc is combined with the polyatomic ion sulfate (SOâ‚„). Sulfate is a common anion formed from sulfur and oxygen atoms. Therefore, the correct name for ZnSOâ‚„ is zinc sulfate. Choice B, Zinc sulfide, is incorrect because sulfide is a different anion (S²â») compared to sulfate (SOâ‚„²â»). Choice C, Zinc sulfur, is incorrect as it does not represent the correct anion in the compound. Choice D, Zinc oxide, is incorrect as it involves an oxygen anion, not sulfate.
How many neutrons are in an atom of carbon-12?
- A. 2
- B. 4
- C. 6
- D. 24
Correct Answer: C
Rationale: An atom of carbon-12 has 6 neutrons. The atomic number of carbon is 6, representing the number of protons. The atomic mass of carbon-12 is 12. To find the number of neutrons, subtract the atomic number from the atomic mass: 12 - 6 = 6 neutrons. Choice A, 2, is incorrect as it does not reflect the correct calculation for neutrons in carbon-12. Choice B, 4, is incorrect as it does not match the correct number of neutrons in carbon-12. Choice D, 24, is incorrect as it is significantly higher than the actual number of neutrons in carbon-12.