HESI A2
Chemistry HESI A2 Quizlet
1. Beta radiation is the product of the decomposition of which particle?
- A. Proton
- B. Neutron
- C. Electron
- D. Photon
Correct answer: B
Rationale: Beta radiation is the result of the decomposition of a neutron. During beta decay, a neutron in an atom's nucleus is transformed into a proton, an electron (beta particle), and an antineutrino. Therefore, the correct answer is 'Neutron.' Choice A, 'Proton,' is incorrect because beta decay does not involve the decomposition of a proton. Choice C, 'Electron,' is incorrect because electrons are actually produced during beta decay. Choice D, 'Photon,' is incorrect as beta radiation does not involve the decomposition of photons.
2. Which number represents the number of protons in an element?
- A. Atomic mass
- B. Mass number
- C. Atomic number
- D. Proton number
Correct answer: C
Rationale: The correct answer is C: Atomic number. The atomic number corresponds to the number of protons in an element. Protons are positively charged subatomic particles found in the nucleus of an atom. Each element has a unique atomic number, which defines its identity based on the number of protons it contains. Choice A, Atomic mass, is incorrect as it refers to the average mass of an atom of an element. Choice B, Mass number, represents the total number of protons and neutrons in an atom's nucleus. Choice D, Proton number, is not a commonly used term in chemistry to indicate the number of protons.
3. What type of chemical reaction involves the reaction of a compound with oxygen?
- A. Decomposition
- B. Synthesis
- C. Combustion
- D. Single replacement
Correct answer: C
Rationale: The correct answer is C: Combustion. A combustion reaction is characterized by a compound reacting with oxygen. During this process, heat and light are often produced as energy is released in the form of heat. Combustion is a common type of reaction involving organic compounds, like hydrocarbons, reacting with oxygen to produce carbon dioxide and water. Choices A, B, and D are incorrect because decomposition involves a compound breaking down into simpler substances, synthesis involves the combination of two or more substances to form a more complex one, and single replacement involves an element replacing another element in a compound.
4. Why does the diffusion rate increase as a substance is heated?
- A. The kinetic energy of particles increases.
- B. The space between particles increases.
- C. The density of particles decreases.
- D. The size of particles increases.
Correct answer: A
Rationale: The correct answer is A. When a substance is heated, the kinetic energy of particles increases, causing them to move faster. This increased movement allows the particles to spread out more rapidly, leading to a higher diffusion rate. Choice B is incorrect because heating does not directly affect the space between particles. Choice C is incorrect because heating does not necessarily lead to a decrease in the density of particles. Choice D is incorrect because the size of particles does not necessarily increase when a substance is heated. Therefore, the correct explanation for the increase in diffusion rate is the rise in kinetic energy of particles.
5. Which compound contains a polar covalent bond?
- A. O
- B. F
- C. Br
- D. H₂O
Correct answer: D
Rationale: The compound 'H₂O' (water) contains a polar covalent bond. In a water molecule, the oxygen atom is more electronegative than the hydrogen atoms. As a result, the electrons in the O-H bonds are unevenly shared, leading to a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. This unequal sharing of electrons creates a polar covalent bond in water. Choices A, B, and C are incorrect because they represent individual elements, not compounds, and do not involve the concept of polar covalent bonds.
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