Nokea
What is the periodic law?
- A. The statement that the properties of the elements are a periodic function of their atomic numbers.
- B. The statement that elements can be arranged in a table where elements with similar properties are grouped together.
- C. The statement that elements can be arranged in a table where the atomic number of an element is equal to the number of protons in its nucleus.
- D. The statement that elements can be arranged in a table where the atomic mass of an element is equal to the number of neutrons in its nucleus.
Correct Answer: A
Rationale: The periodic law states that the properties of elements are a periodic function of their atomic numbers. This means that when elements are arranged in order of increasing atomic number, there is a periodic repetition of their properties. This forms the basis for the modern periodic table. Option B describes the organization of elements in the periodic table, which is related to the periodic law but not the definition of it. Options C and D are incorrect as they describe concepts related to atomic structure (atomic number and atomic mass) rather than the periodic law itself.
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When making a dilution, what do you do?
- A. Add more solvent to a concentrated solution
- B. Change the temperature of the solution
- C. Decrease the concentration of a solution
- D. All of the above
Correct Answer: C
Rationale: When making a dilution, you decrease the concentration of a solution by adding more solvent to a concentrated solution. This process does not involve changing the temperature of the solution, so option B is incorrect. Option A is also incorrect because you are not adding more solute to the solution during dilution. Therefore, the correct answer is C) Decrease the concentration of a solution. Options A and B are incorrect as dilution involves adding more solvent, not solute, and does not require changing the temperature of the solution.
Which of the following is a characteristic of alkenes?
- A. They have a double bond between carbon atoms.
- B. They are saturated hydrocarbons.
- C. They contain only single bonds.
- D. They are derivatives of ammonia.
Correct Answer: A
Rationale: Alkenes are hydrocarbons that contain at least one carbon-carbon double bond. This double bond is a key characteristic that distinguishes alkenes from other types of hydrocarbons. Option A correctly identifies this defining feature of alkenes, making it the correct answer. Choices B, C, and D are incorrect. Choice B is incorrect because alkenes are unsaturated hydrocarbons due to the presence of double bonds. Choice C is incorrect as alkenes do not contain only single bonds; they have at least one double bond. Choice D is incorrect because alkenes are not derivatives of ammonia; they are a distinct class of organic compounds with carbon-carbon double bonds.
What is the name of the regulatory region in a gene that controls its expression?
- A. Exon
- B. Intron
- C. Promoter
- D. Enhancer
Correct Answer: C
Rationale: A) Exon: Exons are the coding regions of a gene that are transcribed into mRNA and eventually translated into proteins. Exons do not regulate gene expression.
B) Intron: Introns are non-coding regions of a gene that are removed during RNA processing and do not play a direct role in controlling gene expression.
C) Promoter: The promoter is a regulatory region located at the beginning of a gene that initiates the process of transcription by binding transcription factors and RNA polymerase. It plays a crucial role in controlling gene expression.
D) Enhancer: Enhancers are regulatory regions that can be located far from the gene they regulate and can increase the transcription of a gene. While enhancers are important for gene expression, the specific region that controls gene expression is the promoter.
Therefore, the correct answer is C) Promoter, as it is the regulatory region in a gene that controls its expression by initiating transcription.
Which of the following is the positively charged subatomic particle found in the nucleus of an atom?
- A. Electron
- B. Proton
- C. Neutron
- D. Quark
Correct Answer: B
Rationale: The correct answer is B: Proton. Protons are positively charged subatomic particles found in the nucleus of an atom. They have a mass of approximately 1 atomic mass unit (amu) and a charge of +1. The number of protons in an atom's nucleus determines the atomic number of the element, which is a unique identifier for each element. Choice A, Electron, is incorrect as electrons are negatively charged particles found outside the nucleus. Choice C, Neutron, is incorrect as neutrons are neutral particles found in the nucleus. Choice D, Quark, is incorrect as quarks are elementary particles that combine to form protons and neutrons, but they are not the positively charged particle found in the nucleus of an atom.
Passive transport does not require energy input from the cell. Which of the following is an example of passive transport?
- A. Active transport of ions across a membrane
- B. Diffusion of small molecules across a concentration gradient
- C. Movement of large molecules using vesicles
- D. Endocytosis of particles into the cell
Correct Answer: B
Rationale: Passive transport refers to the movement of molecules across a cell membrane without the input of energy. Diffusion of small molecules across a concentration gradient is a classic example of passive transport, as it occurs spontaneously from an area of high concentration to an area of low concentration. Active transport (option A) requires energy input in the form of ATP to move substances against their concentration gradient. Movement of large molecules using vesicles (option C) involves processes like endocytosis and exocytosis that require energy in the form of ATP. Endocytosis of particles into the cell (option D) is an active process that requires energy expenditure by the cell to engulf and internalize extracellular substances.