HESI A2
Chemistry HESI A2 Quizlet
1. What type of reaction involves atoms attempting to achieve stable electron configurations?
- A. Chemical
- B. Nuclear
- C. Physical
- D. Mechanical
Correct answer: A
Rationale: In a chemical reaction, atoms interact to achieve stable electron configurations through the formation of new chemical bonds or the breaking of existing ones. This process aims to reach a more stable state by filling or emptying electron orbitals, leading to the formation of new substances with more stable configurations. Choice B, nuclear reactions, involve changes in the atomic nucleus rather than electron configurations. Choice C, physical reactions, involve changes in physical state or appearance without changing the chemical makeup. Choice D, mechanical reactions, do not involve the rearrangement of electrons to achieve stable configurations.
2. Which of the following pH values is most likely for lemon juice?
- A. 3
- B. 5
- C. 7
- D. 9
Correct answer: A
Rationale: Lemon juice is highly acidic with a pH around 2-3, making it more acidic than neutral substances. A pH of 5 is too high for lemon juice, indicating less acidity. Similarly, pH 7 is neutral, and pH 9 would be alkaline, which is not characteristic of lemon juice. Therefore, the correct answer is option A (pH 3).
3. Which element has the highest atomic number?
- A. Uranium
- B. Hydrogen
- C. Radon
- D. Bismuth
Correct answer: A
Rationale: The correct answer is Uranium. The atomic number represents the number of protons in an atom's nucleus. Among the options provided, Uranium has the highest atomic number, which is 92. Hydrogen has an atomic number of 1, Radon has an atomic number of 86, and Bismuth has an atomic number of 83. Therefore, Uranium is the element with the highest atomic number in the given choices.
4. What is the name of the negatively charged subatomic particles?
- A. Protons
- B. Neutrons
- C. Electrons
- D. Isotopes
Correct answer: C
Rationale: The correct answer is C: Electrons. Electrons are the negatively charged subatomic particles. They are found outside the atomic nucleus and carry a negative charge. Protons are positively charged particles found in the nucleus, neutrons have no charge, and isotopes are atoms of the same element with different numbers of neutrons, not subatomic particles.
5. How does increasing the concentration of reactants affect a chemical reaction?
- A. Decreases the reaction rate
- B. Increases the reaction rate
- C. Stops the reaction
- D. Has no effect
Correct answer: B
Rationale: Increasing the concentration of reactants leads to more reactant particles being available, which, in turn, increases the likelihood of successful collisions between particles. This higher frequency of collisions results in a higher reaction rate. Therefore, option B, 'Increases the reaction rate,' is the correct answer. Choice A, 'Decreases the reaction rate,' is incorrect because higher reactant concentration usually speeds up the reaction. Choice C, 'Stops the reaction,' is incorrect as increasing concentration promotes more collisions, enhancing the reaction. Choice D, 'Has no effect,' is incorrect because changing reactant concentration directly impacts the reaction rate in most cases.
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