Nokea
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.
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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.
Identify the reactants in the chemical reaction below: CH₄ + 2O₂ → CO₂ + 2H₂O
- A. CHâ‚„ and Oâ‚‚
- B. COâ‚‚ and Hâ‚‚O
- C. Both
- D. None of the above
Correct Answer: A
Rationale: Reactants in a chemical reaction are the initial substances that are transformed into products. In this reaction, CHâ‚„ (methane) and Oâ‚‚ (oxygen) are the reactants, as they are the starting materials that undergo a chemical change to form COâ‚‚ (carbon dioxide) and 2Hâ‚‚O (water). The equation clearly shows that CHâ‚„ and Oâ‚‚ are on the left side of the reaction arrow, indicating that they are the reactants. Therefore, the correct answer is A: CHâ‚„ and Oâ‚‚.
What volume of silver will weigh exactly 2500.0 g? The density of silver is 10.5 g/cm³.
- A. 262.50 cm³
- B. 238.1 cm³
- C. 0.0042 cm³
- D. None of the above
Correct Answer: B
Rationale: To find the volume of silver, we use the formula: Volume = Mass / Density. Plugging in the given values, Volume = 2500.0 g / 10.5 g/cm³ = 238.1 cm³. Therefore, the correct answer is 238.1 cm³, which corresponds to option B.
An element has 6 protons, 6 electrons, and 6 neutrons. What is its atomic number?
- A. 6
- B. 12
- C. 18
- D. Not enough information
Correct Answer: A
Rationale: The atomic number of an element is determined by the number of protons in its nucleus. Since the element in question has 6 protons, its atomic number is also 6. The number of neutrons and electrons does not impact the atomic number, which is solely based on the number of protons. Therefore, the correct answer is A: 6.
What is 119°K in degrees Celsius?
- A. 32°C
- B. -154°C
- C. 154°C
- D. -32°C
Correct Answer: B
Rationale: The correct answer is 'B: -154°C.' To convert Kelvin to Celsius, you subtract 273.15 from the temperature in Kelvin. For 119°K: 119 - 273.15 = -154.15. Thus, 119°K is equal to approximately -154°C.