Nokea
Will solids always sink in liquids?
- A. True, because solids are hard while liquids are not.
- B. True, because solids are heavier than liquids.
- C. False, because solids have a smooth surface, so they will float.
- D. False, it depends on the density of the solid and liquid.
Correct Answer: D
Rationale: The statement 'solids will always sink in liquids' is not always true. Whether a solid sinks or floats in a liquid depends on the relative densities of the solid and the liquid. If the density of the solid is greater than the density of the liquid, the solid will sink. Conversely, if the density of the solid is less than the density of the liquid, the solid will float. Therefore, the correct answer is 'False, it depends on the density of the solid and liquid.'
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The chemical equation Cr + Fe(NO₃)₂ → Fe + Cr(NO₃)₂ is an example of which type of reaction?
- A. Single replacement
- B. Decomposition
- C. Double replacement
- D. Combustion
Correct Answer: A
Rationale: The correct answer is A: Single replacement. In this reaction, chromium (Cr) replaces iron (Fe) in the compound Fe(NO₃)₂, resulting in the formation of Fe and Cr(NO₃)₂. Single replacement reactions involve an element and a compound, where the element replaces another element in the compound. The general form of a single replacement reaction is A + BC → AC + B, where A is an element and BC is a compound. This type of reaction is also known as a displacement reaction, where a more reactive element displaces a less reactive element in a compound.
Which of the following is not an organic compound?
- A. Hâ‚‚O
- B. C₂H₆
- C. C₃H₇O₂
- D. None of the above
Correct Answer: A
Rationale: The correct answer is 'A: H₂O.' An organic compound is defined as a compound that contains carbon and hydrogen atoms bonded together. Choice A, H₂O (water), is composed of hydrogen and oxygen but lacks carbon, making it an inorganic compound. Choices B (C₂H₆) and C (C₃H₇O₂) both contain carbon and hydrogen, thus meeting the criteria for organic compounds. Therefore, the correct answer is A, H₂O, as it does not meet the definition of an organic compound due to the absence of carbon in its structure.
An atom has a mass of 16 and 6 protons. What element is it, and how many neutrons are there?
- A. Sulfur, 10
- B. Sulfur, 22
- C. Carbon, 10
- D. Carbon, 22
Correct Answer: C
Rationale: The atomic mass of an atom is the sum of its protons and neutrons. In this case, the atom has 6 protons. To find the number of neutrons, subtract the number of protons (6) from the atomic mass (16), resulting in 10 neutrons. Since the atom with 6 protons corresponds to Carbon (which has an atomic number of 6), the correct answer is Carbon, 10.
Which type of reaction is most likely represented by the products CO2 + H2O: CO2 + H2O?
- A. Synthesis
- B. Decomposition
- C. Single replacement
- D. Combustion
Correct Answer: D
Rationale: The reaction products CO2 and H2O suggest a combustion reaction. In a combustion reaction, a substance reacts with oxygen gas (O2) to produce carbon dioxide (CO2) and water (H2O) as products. The given reaction matches the characteristic products of a combustion reaction, indicating that option D, 'Combustion,' is the correct answer.
In the chemical reaction CH₄ + 2O₂ → CO₂ + 2H₂O, what are the reactants?
- A. CHâ‚„ and Oâ‚‚
- B. COâ‚‚ and Hâ‚‚O
- C. Both
- D. None of the above
Correct Answer: A
Rationale: The correct answer is 'A: CHâ‚„ and Oâ‚‚.' Reactants are the substances that undergo a change to form the products in a chemical reaction. In the given reaction, CHâ‚„ (methane) and Oâ‚‚ (oxygen) are the reactants, as they transform into COâ‚‚ and 2Hâ‚‚O, which are the products. Therefore, the correct answer is A.