HESI A2
Chemistry HESI A2 Quizlet
1. What type of chemical reaction involves the combination of two elements to form a product?
- A. Decomposition
- B. Combustion
- C. Synthesis
- D. Double replacement
Correct answer: C
Rationale: A synthesis reaction involves the combination of two or more substances to form a single, more complex product. In the context of chemical reactions, it specifically refers to the combination of two elements to form a compound. Therefore, the correct answer is C. Decomposition reactions involve the breakdown of a single compound into simpler substances (opposite of synthesis). Combustion reactions involve a substance reacting with oxygen to produce heat and light, not the combination of elements. Double replacement reactions involve the exchange of ions between two compounds, leading to the formation of two new compounds, not the combination of two elements.
2. What determines polarity in a molecule?
- A. Bond length
- B. Bond strength
- C. Electronegativity
- D. Molecular weight
Correct answer: C
Rationale: Polarity in a molecule is determined by the difference in electronegativity between the atoms forming the bond. The greater the difference in electronegativity, the more polar the bond and molecule become. This difference leads to an uneven distribution of electron density within the bond, creating partial positive and negative charges on the atoms involved. Choices A, B, and D are incorrect. Bond length and strength do not determine polarity, and molecular weight is not directly related to the polarity of a molecule.
3. What charge do Group VIA elements typically have?
- A. -1
- B. -2
- C. -3
- D. 0
Correct answer: B
Rationale: Group VIA elements, also known as Group 16 elements, typically have a charge of -2. This is because they have 6 valence electrons and tend to gain 2 electrons to achieve a stable octet configuration, resulting in a -2 charge. Choice A (-1) is incorrect as Group VIA elements need to gain 2 electrons for stability, not just 1. Choice C (-3) is incorrect because Group VIA elements do not need to gain 3 electrons to achieve stability. Choice D (0) is incorrect as Group VIA elements need to gain electrons to reach a stable configuration, resulting in a negative charge.
4. Which factor does not affect the reaction rate of a chemical reaction?
- A. Temperature
- B. Surface area
- C. Concentration of reactants
- D. Color of the reactants
Correct answer: D
Rationale: The color of reactants is not a factor that affects the rate of a chemical reaction. Temperature, surface area, and concentration of reactants are known factors that influence the reaction rate. Temperature plays a significant role in altering the reaction rate by affecting the kinetic energy of molecules. Surface area impacts the rate by providing more area for collisions to occur. Concentration affects the frequency of effective collisions. On the other hand, the color of reactants is a physical property that does not directly affect the speed of a chemical reaction.
5. What charge do Group IIA elements typically have?
- A. 1
- B. +2
- C. -3
- D. 0
Correct answer: B
Rationale: Group IIA elements belong to the alkaline earth metals group in the periodic table. These elements typically have a charge of +2 because they readily lose two electrons to achieve a stable electron configuration. Therefore, the correct answer is B - +2. Choice A (1) is incorrect because Group IIA elements lose two electrons, not one. Choice C (-3) is incorrect because Group IIA elements do not gain electrons to have a negative charge. Choice D (0) is incorrect because Group IIA elements do lose electrons and have a positive charge, not a neutral charge.
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