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Which of the following is a balanced chemical equation?
- A. H2 + O2 → H2O
- B. 2H2 + O2 → 2H2O
- C. 3H2O → 2H2 + O2
- D. H2O → H2 + O2
Correct Answer: B
Rationale: A balanced chemical equation must have the same number of atoms of each element on both sides of the equation. In option B, 2H2 + O2 → 2H2O, the equation is balanced as there are 2 hydrogen atoms and 2 oxygen atoms on both the reactant and product sides after balancing, satisfying the law of conservation of mass. Option A is unbalanced as there are 2 oxygen atoms on the reactant side but only 1 oxygen atom on the product side. Option C is unbalanced with 3 hydrogen atoms on the reactant side and 2 hydrogen atoms on the product side. Option D is unbalanced with 1 oxygen atom on the reactant side and 2 oxygen atoms on the product side.
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Which of the following situations represents work being done on an object?
- A. Pushing against a wall without moving it
- B. Carrying a heavy object without lifting it
- C. Lifting a box to place it on a shelf
- D. Holding a book stationary in your hand
Correct Answer: C
Rationale: Work is defined as the product of the force applied to an object and the distance over which the force is applied. In the situation of lifting a box to place it on a shelf, work is being done on the object. This is because lifting the box involves applying a force over a distance (the height of the shelf). The force applied to lift the box results in work being done on the object by raising it against the force of gravity. Choices A, B, and D do not involve work being done on the object as they either do not involve movement against a force (A, D) or do not cover distance against a force (B).
Which of the following is an example of a decomposition reaction?
- A. 2H2 + O2 → 2H2O
- B. CaCO3 → CaO + CO2
- C. 2Na + Cl2 → 2NaCl
- D. N2 + 3H2 → 2NH3
Correct Answer: B
Rationale: A decomposition reaction involves a single compound breaking down into two or more simpler substances. In option B, CaCO3 breaks down into CaO and CO2, making it an example of a decomposition reaction. Options A, C, and D involve different types of chemical reactions such as synthesis, combination, and combustion, respectively. Option A represents a synthesis reaction, where two elements combine to form a compound. Option C demonstrates a combination reaction, where two elements combine to form a compound. Option D is an example of a synthesis reaction, where two reactants combine to form a single compound. It is important to recognize the specific characteristics of each type of chemical reaction to identify the correct example of decomposition reaction, where a compound breaks down into simpler products.
What is the name for the smallest amount of an element that can exist independently and retain its chemical properties?
- A. Atom
- B. Molecule
- C. Compound
- D. Mixture
Correct Answer: A
Rationale: The correct answer is 'Atom.' An atom is the fundamental unit of an element that can exist independently and retain its unique chemical properties. It consists of a nucleus containing protons and neutrons, surrounded by electrons. Choice B, 'Molecule,' is incorrect because a molecule is a combination of two or more atoms bonded together. Choice C, 'Compound,' is incorrect as a compound is a substance formed by the chemical combination of two or more different elements. Choice D, 'Mixture,' is incorrect since a mixture is a blend of two or more substances physically combined, but the individual components retain their properties.
Which of the following blood vessels carries oxygenated blood from the lungs to the heart?
- A. Pulmonary vein
- B. Pulmonary artery
- C. Aorta
- D. Vena cava
Correct Answer: A
Rationale: The correct answer is A: Pulmonary vein. The pulmonary vein carries oxygenated blood from the lungs to the heart. It is essential to distinguish between the pulmonary vein (A) and the pulmonary artery (B) in this context. The pulmonary vein transports oxygenated blood, while the pulmonary artery carries deoxygenated blood from the heart to the lungs for oxygenation. The aorta (C) functions as the main artery that delivers oxygenated blood from the heart to the body's tissues, while the vena cava (D) returns deoxygenated blood from the body to the heart.
What is the primary function of the coronary arteries in the cardiovascular system?
- A. Carry oxygenated blood to the heart muscle
- B. Carry deoxygenated blood from the heart muscle
- C. Pump blood to the lungs for oxygenation
- D. Regulate blood pressure in the systemic circulation
Correct Answer: A
Rationale: The primary function of the coronary arteries is to carry oxygenated blood to the heart muscle. Oxygenated blood is crucial for providing nutrients and oxygen to the heart muscle cells, enabling the heart to work efficiently. Without this oxygenated blood supply, the heart muscle may not receive the required nutrients and oxygen, potentially resulting in heart damage or dysfunction. Choices B, C, and D are incorrect as coronary arteries do not carry deoxygenated blood from the heart muscle, pump blood to the lungs for oxygenation, or regulate blood pressure in the systemic circulation. The coronary arteries specifically supply oxygenated blood to the heart muscle to support its function and vitality.