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How many moles of oxygen are required to completely react with 5 moles of propane (C3H8) in the combustion reaction?
- A. 5 moles
- B. 10 moles
- C. 15 moles
- D. 20 moles
Correct Answer: C
Rationale: In the balanced chemical equation for the combustion of propane (C3H8): C3H8 + 5O2 → 3CO2 + 4H2O, 1 mole of propane (C3H8) reacts with 5 moles of oxygen (O2). To determine the moles of oxygen required to react with 5 moles of propane, we use the molar ratio: 5 moles propane x 5 moles oxygen / 1 mole propane = 25 moles oxygen. However, since the question specifically asks for the moles of oxygen needed to react with 5 moles of propane, the correct answer is 15 moles of oxygen. Choice A, 5 moles, is incorrect because this is the amount of propane provided, not the oxygen required. Choice B, 10 moles, is incorrect as it does not correspond to the molar ratio in the balanced equation. Choice D, 20 moles, is incorrect as it is not in line with the stoichiometry of the reaction.
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What is the involuntary muscle tissue found in the walls of blood vessels and organs like the stomach and intestines?
- A. Skeletal muscle
- B. Cardiac muscle
- C. Smooth muscle
- D. Striated muscle
Correct Answer: C
Rationale: Smooth muscle is the correct answer. It is the involuntary muscle tissue found in the walls of blood vessels and organs like the stomach and intestines. Smooth muscle is responsible for various involuntary movements in the body, such as peristalsis in the digestive system and regulating blood flow in blood vessels. Skeletal muscle is voluntary and attached to bones for movement. Cardiac muscle is specific to the heart and not found in blood vessel walls or organs like the stomach and intestines. Striated muscle refers to both skeletal and cardiac muscle due to their striped appearance under a microscope, but it does not specifically describe the involuntary muscle tissue in the walls of blood vessels and organs as asked in the question.
What is the primary function of the atrioventricular (AV) node within the heart?
- A. Generate the electrical impulse for contraction (pacemaker function)
- B. Transmit the electrical impulse from the atria to the ventricles, regulating the timing of contraction.
- C. Increase blood pressure within the ventricles during systole.
- D. Separate oxygenated and deoxygenated blood flow in the heart.
Correct Answer: B
Rationale: The correct answer is B: Transmit the electrical impulse from the atria to the ventricles, regulating the timing of contraction. The primary function of the atrioventricular (AV) node is to coordinate the transmission of electrical signals between the atria and the ventricles. It ensures proper timing between atrial and ventricular contractions, allowing for efficient blood pumping through the heart. Choice A is incorrect because the AV node does not generate the initial electrical impulse; that role is typically attributed to the sinoatrial (SA) node. Choice C is incorrect as the AV node does not directly influence blood pressure within the ventricles. Choice D is also incorrect as the separation of oxygenated and deoxygenated blood is primarily achieved by the anatomical structure of the heart (e.g., atria and ventricles) and not the AV node.
Which property of a substance refers to its ability to be hammered or pressed into thin sheets without breaking?
- A. Malleability
- B. Ductility
- C. Viscosity
- D. Conductivity
Correct Answer: A
Rationale: Malleability is the correct answer as it is the property of a substance that allows it to be hammered or pressed into thin sheets without breaking. This property is crucial for materials like metals that need to be shaped without breaking. Ductility, on the other hand, refers to the ability of a substance to be drawn into thin wires, not hammered into sheets. Viscosity is a measure of a fluid's resistance to flow, indicating its thickness or thinness, and is unrelated to the ability to be hammered. Conductivity, on the other hand, refers to a substance's ability to conduct electricity or heat, which is not related to its ability to be hammered or pressed into thin sheets.
What is the basic unit of communication in the nervous system?
- A. Neuron
- B. Astrocyte
- C. Neurotransmitter
- D. Synapse
Correct Answer: A
Rationale: A neuron is the basic unit of communication in the nervous system. Neurons are specialized cells responsible for transmitting information through electrical and chemical signals. Astrocytes are a type of glial cell that provide support and nourishment to neurons but do not participate in signal transmission. Neurotransmitters are chemicals that facilitate signal transmission between neurons, and synapses are the specific junctions where these signals are transmitted. Therefore, the correct answer is 'A: Neuron' as it is the primary cell involved in transmitting information in the nervous system.
What is the scientific term for scar tissue?
- A. Epithelial tissue
- B. Fibrous connective tissue
- C. Cartilage
- D. Adipose tissue
Correct Answer: B
Rationale: The correct scientific term for scar tissue is fibrous connective tissue. Scar tissue is primarily composed of fibrous connective tissue, which forms as part of the body's natural healing process in response to injury or trauma. Epithelial tissue, cartilage, and adipose tissue are not typically involved in scar formation. Therefore, the correct answer is fibrous connective tissue, as it is the specific type of tissue that makes up scar tissue.