Nokea
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.
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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.
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.
How many hydrogen atoms are present in the reactants?
- A. 2
- B. 4
- C. 1
- D. None of the above
Correct Answer: B
Rationale: To determine the number of hydrogen atoms in the reactants, we need to examine the chemical formula of the reactants. If the formula contains hydrogen atoms, we count them to find the total. In this case, the correct answer is 4 because there are 4 hydrogen atoms present in the reactants. The chemical formula in the reactants indicates the presence of 4 hydrogen atoms. It is crucial to pay close attention to the elements and their quantities in chemical reactions to ensure accurate analysis and understanding of reactants and products.
What can be predicted by using the periodic table?
- A. The properties of each element
- B. The charges of polyatomic ions
- C. The number of isotopes for each element
- D. The potential for discovering new elements
Correct Answer: A
Rationale: The periodic table organizes elements based on their properties, such as atomic number, electron configuration, and chemical behavior. By examining an element's position on the periodic table, one can predict its properties, including its physical and chemical characteristics, reactivity, and other behaviors. This predictive ability is one of the fundamental strengths of the periodic table in understanding and working with elements. Therefore, the correct answer is A, as the periodic table allows for the prediction of the properties of each element based on its location and characteristics within the table.
Which of the following statements is most accurate regarding the compound 2Hâ‚‚O?
- A. 2Hâ‚‚O has a total of 2 hydrogen atoms.
- B. 2Hâ‚‚O represents two water molecules.
- C. Hâ‚‚O represents two water molecules.
- D. None of the above.
Correct Answer: B
Rationale: The chemical formula 2Hâ‚‚O represents two water molecules. Each water molecule (Hâ‚‚O) consists of 2 hydrogen atoms and 1 oxygen atom. Therefore, 2Hâ‚‚O denotes two separate water molecules, making choice B the correct statement