Nokea
Which statement is true regarding combination reactions?
- A. Involve only one reactant.
- B. Involve an element and an ionic compound.
- C. Form only one product.
- D. Require oxygen gas.
Correct Answer: C
Rationale: In a combination reaction, two or more substances combine to form a single product. This reaction type does not always involve only one reactant (choice A), an element and an ionic compound (choice B), or require oxygen gas (choice D). The true characteristic of combination reactions is that they form only one product, making choice C the correct answer.
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Which element has 13 protons, 13 electrons, and 14 neutrons?
- A. Fe
- B. Zr
- C. Al
- D. Not enough information
Correct Answer: C
Rationale: The element with 13 protons is Aluminum (Al), as the atomic number of an element is determined by the number of protons. The total number of protons and neutrons in an element's nucleus is known as the mass number. Given that the mystery element has 13 protons and 14 neutrons, it matches the characteristics of Aluminum, making it 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.
Which subatomic particle does not contribute significantly to an atom's mass?
- A. Proton
- B. Neutron
- C. Electron
- D. All contribute to the atom's mass.
Correct Answer: C
Rationale: Electrons do not contribute significantly to an atom's mass. Protons and neutrons are much more massive than electrons and make up the majority of an atom's mass. Electrons have a very small mass compared to protons and neutrons, and their contribution to the total mass of an atom is considered negligible. Therefore, the correct answer is C, Electrons.
Which of the following could be an empirical formula?
- A. C4H8
- B. C2H6
- C. CH
- D. C3H6
Correct Answer: C
Rationale: An empirical formula represents the simplest whole-number ratio of atoms in a compound. For a hydrocarbon compound consisting of carbon and hydrogen, the empirical formula should have the simplest ratio of carbon to hydrogen. Choice C, 'CH,' is the correct empirical formula as it represents a 1:1 ratio of carbon to hydrogen atoms, indicating the simplest ratio. Choices A, B, and D have multiple atoms of carbon and hydrogen, which do not represent the simplest whole-number ratio. Therefore, 'CH' is the empirical formula that best fits the definition.
What is the atomic number of a mystery element that has 6 protons, 6 electrons, and 6 neutrons?
- A. 6
- B. 12
- C. 18
- D. Not enough information
Correct Answer: A
Rationale: The atomic number of an element is equal to the number of protons in its nucleus. Since the mystery element has 6 protons, its atomic number is also 6. The number of neutrons and electrons does not affect the atomic number. Protons determine the element's identity, while neutrons and electrons affect its mass and charge, respectively. Therefore, choice A, 6, is the correct answer.