Nokea
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‚‚.
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What is the density of iron when 28.5g of iron shot 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 determine the density of iron, we use the formula: Density = Mass / Volume. The mass of the iron is given as 28.5g. The volume of water displaced by the iron is the final volume (49.1mL) minus the initial volume (45.5mL), resulting in 3.6mL. Therefore, the density of iron can be calculated by dividing the mass of iron (28.5g) by the volume of water displaced (3.6mL), giving us 7.92 g/mL. Therefore, choice B, 7.92 g/mL, is the correct answer.
What is the term for the reactant that is entirely consumed in a reaction?
- A. limiting reactant
- B. reducing agent
- C. reaction intermediate
- D. reagent
Correct Answer: A
Rationale: The term for the reactant that is entirely consumed in a reaction is the limiting reactant. The limiting reactant is crucial in determining the maximum amount of product that can be formed as it is fully consumed in the reaction. The other choices, reducing agent, reaction intermediate, and reagent, do not specifically refer to the reactant that is completely consumed during the reaction process. Identifying the limiting reactant is essential for calculating the theoretical yield of a reaction and understanding the stoichiometry of the reaction.
What is the pH of a solution with a pH of 7?
- A. Acidic
- B. Basic
- C. Neutral
- D. Positive
Correct Answer: C
Rationale: The correct answer is C: Neutral. A pH of 7 is considered neutral on the pH scale, which ranges from 0 to 14. A pH of 7 indicates a balance between acidic and basic properties in a solution, making it neither acidic nor basic. Values below 7 are acidic, above 7 are basic, and 7 is the midpoint representing neutrality. Therefore, a solution with a pH of 7 is neutral.
What is the mass of ethyl alcohol that exactly fills a 200.0 mL container?
- A. 157.8 g
- B. 253.49 g
- C. 0.0039 g
- D. None of the above
Correct Answer: A
Rationale: To determine the mass of ethyl alcohol that fills a 200.0 mL container, we use the formula: Mass = Volume x Density. Given that the density of ethyl alcohol is 0.789 g/mL, multiplying the volume (200.0 mL) by the density gives us 200.0 mL x 0.789 g/mL = 157.8 g. Therefore, the correct answer is A, 157.8 g, representing the mass of ethyl alcohol that exactly fills the 200.0 mL container.
Where are protons held within an atom?
- A. Nucleus
- B. Orbitals
- C. Electron cloud
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Nucleus. Protons are held in the nucleus, the central part of an atom where both protons and neutrons are located. Protons carry a positive charge and are specifically found within the nucleus. Orbitals and the electron cloud are regions where electrons are located surrounding the nucleus, not protons. Understanding the basic structure of an atom is fundamental in chemistry, where the nucleus serves as the core that contains the majority of the atom's mass and positive charge due to the presence of protons. This knowledge is crucial for grasping various chemical concepts and explaining the behavior of elements in chemical reactions.