Nokea
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.
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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.
Which type of RNA is used to carry the genetic code copied from DNA?
- A. mRNA
- B. tRNA
- C. rRNA
- D. None of the above
Correct Answer: A
Rationale: The correct answer is mRNA (messenger RNA). mRNA is responsible for carrying the genetic information copied from DNA in the cell nucleus to the ribosomes in the cytoplasm where protein synthesis occurs. This process is known as transcription. mRNA acts as a messenger, delivering the genetic instructions to the ribosomes for protein synthesis. In contrast, tRNA (transfer RNA) brings specific amino acids to the ribosome during translation, helping to assemble the protein chain. rRNA (ribosomal RNA) forms a structural and catalytic part of the ribosome itself, aiding in protein synthesis. Therefore, among the options provided, mRNA is the RNA type directly involved in carrying the genetic code from DNA for protein production.
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.
In a double replacement reaction, which of the following occurs?
- A. Energy in the form of heat or light is often produced.
- B. The reactants are usually a metal and a nonmetal.
- C. A gas, solid precipitate, or compound forms in the exchange of ions.
- D. All statements are true.
Correct Answer: C
Rationale: In a double replacement reaction, the cations and anions of two compounds switch places to form two new compounds. During this process, a gas, solid precipitate, or compound can be formed as the exchange of ions occurs. This often results in the formation of a new product that is insoluble and forms a solid precipitate, a gas that bubbles out, or a compound that remains in the solution. Therefore, choice C is correct as it accurately describes the typical outcomes of a double replacement reaction.
What characterizes bases or alkaline solutions?
- A. Hydrogen acceptors
- B. Solutions of low pH
- C. Hydrogen donors
- D. Amphoteric
Correct Answer: A
Rationale: Bases or alkaline solutions are characterized by their ability to accept protons (hydrogen ions), making them hydrogen acceptors. When a base reacts with an acid, it accepts protons from the acid, forming water and a salt. This property distinguishes bases from acids, which donate protons. Therefore, the correct choice is A, as bases do not donate protons but instead accept them. This property allows bases to neutralize acids and regulate pH levels in solutions, making them crucial in maintaining the balance of acidity and alkalinity in various chemical systems.