Nokea
A carbon atom with fewer neutrons than a neutral carbon atom is known as what?
- A. Isotope
- B. Ion
- C. Both are correct
- D. None of the above
Correct Answer: A
Rationale: The correct answer is 'Isotope.' An isotope is a variant of a chemical element that has the same number of protons but a different number of neutrons in its nucleus. In this scenario, a carbon atom with fewer neutrons than a neutral carbon atom represents a different isotope of carbon with a distinct atomic mass. The difference in neutron count does not alter the atom's charge, ruling out the possibility of it being an ion. Therefore, the appropriate term to describe this situation is 'Isotope.'
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What is the density of iron if 28.5g of iron is added to a graduated cylinder containing 45.5mL of water, causing the water level to rise to the 49.1mL mark?
- A. 0.63 g/mL
- B. 7.92 g/mL
- C. 0.58 g/mL
- D. None of the above.
Correct Answer: B
Rationale: To calculate density, divide mass by volume. First, determine the volume of iron added by subtracting the initial volume of water from the final volume with iron. The volume of iron is calculated as 49.1mL - 45.5mL = 3.6mL. Density of iron is then determined as the mass of iron divided by the volume of iron, which equals 28.5g / 3.6mL = 7.92 g/mL. Therefore, the correct answer is B, 7.92 g/mL.
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.
What are buffers?
- A. Proteins
- B. Solutions that resist changes in pH
- C. Catalysts in a reaction
- D. Inhibitors in a reaction
Correct Answer: B
Rationale: Buffers are solutions that resist changes in pH by neutralizing small amounts of acids or bases that may be added to them. They help maintain a stable pH environment and are commonly used in various biological and chemical processes to prevent drastic changes in acidity or alkalinity. Buffers do not act as catalysts or inhibitors in reactions. Their main purpose is to stabilize pH levels and ensure a relatively constant pH within a system, making them essential in maintaining the proper conditions for many biological reactions and processes.
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.
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.