Nokea
What information can be obtained directly from the element's atomic number?
- A. Its atomic mass
- B. Its position on the periodic table
- C. Its number of neutrons
- D. Its chemical properties
Correct Answer: B
Rationale: The atomic number of an element represents the number of protons in the nucleus of an atom. This number determines the element's unique identity and its position on the periodic table. The atomic mass (option A) is not directly determined by the atomic number but is a weighted average of the isotopes of an element. The number of neutrons (option C) is not directly provided by the atomic number but can be calculated by subtracting the atomic number from the atomic mass. The position on the periodic table (option B) is directly related to the atomic number, as elements are arranged in order of increasing atomic number. The chemical properties of an element (option D) are influenced by the number of protons in the nucleus, which is determined by the atomic number.
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Which type of bond involves the complete transfer of electrons between atoms?
- A. Covalent bond
- B. Ionic bond
- C. Metallic bond
- D. Hydrogen bond
Correct Answer: B
Rationale: The correct answer is B, Ionic bond. Ionic bond involves the complete transfer of electrons from one atom to another, resulting in the formation of cations and anions. This transfer leads to the creation of strong electrostatic attraction between the oppositely charged ions. Covalent bonds, on the other hand, involve the sharing of electrons between atoms to achieve stability. Metallic bonds are formed in metals, where a sea of delocalized electrons surrounds positively charged metal ions, contributing to the metal's properties. Hydrogen bonds are intermolecular forces that occur between a hydrogen atom and a highly electronegative atom like oxygen or nitrogen, not involving the complete transfer of electrons.
What is the term for the balanced equation that represents a chemical reaction?
- A. Hypothesis
- B. Chemical formula
- C. Balanced equation
- D. Reaction mechanism
Correct Answer: C
Rationale: The correct answer is C - 'Balanced equation'. A balanced equation is a representation of a chemical reaction that shows the reactants, products, and their stoichiometric coefficients. It ensures that the number of atoms of each element is equal on both sides of the equation, following the law of conservation of mass. Choice A, 'Hypothesis', is incorrect as it refers to a proposed explanation based on limited evidence as a starting point for further investigation. Choice B, 'Chemical formula', is incorrect as it represents the composition of a compound using symbols and subscripts. Choice D, 'Reaction mechanism', is incorrect as it describes the step-by-step process by which a chemical reaction occurs, not just the overall representation of the reaction itself.
What is the name of the cartilage flap that covers the trachea during swallowing, preventing food from entering the airway?
- A. Epiglottis
- B. Glottis
- C. Larynx
- D. Pharynx
Correct Answer: A
Rationale: The correct answer is A: Epiglottis. The epiglottis is a cartilage flap located at the base of the tongue that covers the trachea during swallowing. Its primary function is to prevent food and liquids from entering the airway and instead directs them towards the esophagus. The glottis (choice B) refers to the space between the vocal cords in the larynx. The larynx (choice C) is the voice box containing the vocal cords responsible for phonation. The pharynx (choice D) is the throat region connecting the mouth and the esophagus, playing a role in both digestion and respiration.
Where in the cell are proteins modified, sorted, and packaged for transport?
- A. Ribosomes
- B. Golgi apparatus
- C. Endoplasmic reticulum (ER)
- D. Lysosomes
Correct Answer: B
Rationale: The Golgi apparatus is the cellular organelle responsible for modifying, sorting, and packaging proteins for transport within the cell or for secretion outside the cell. Ribosomes are not involved in modifying, sorting, or packaging proteins; they are responsible for protein synthesis. The endoplasmic reticulum (ER) is primarily involved in protein synthesis and folding, rather than modification and packaging for transport. Lysosomes function in breaking down cellular waste rather than modifying, sorting, or packaging proteins for transport.
Imagine you have an element with atomic number 11 and mass number 23. How many neutrons does it have?
- A. 11
- B. 12
- C. 23
- D. 21
Correct Answer: B
Rationale: - The atomic number (Z) of an element is the number of protons in its nucleus. In this case, the element has an atomic number of 11.
- The mass number (A) of an element is the sum of its protons and neutrons. Given that the mass number is 23 and the atomic number is 11, we can calculate the number of neutrons by subtracting the atomic number from the mass number: Neutrons = Mass number - Atomic number = 23 - 11 = 12.
- Therefore, the element with atomic number 11 and mass number 23 has 12 neutrons.