HESI A2
Chemistry HESI A2 Quizlet
1. Which type of radiation involves the emission of helium ions?
- A. Beta
- B. Alpha
- C. Gamma
- D. Delta
Correct answer: B
Rationale: Alpha radiation involves the emission of helium ions. Helium ions are composed of two protons and two neutrons, which is the same as the nucleus of a helium atom. This type of radiation has low penetration power and can be stopped by a piece of paper or human skin, making it less harmful compared to other forms of radiation like beta or gamma radiation. Beta radiation involves the emission of high-speed electrons, while gamma radiation involves electromagnetic waves with high energy. Delta radiation is not a recognized form of radiation in this context, making it an incorrect choice.
2. Which element has the highest electronegativity?
- A. Fluorine
- B. Chlorine
- C. Nitrogen
- D. Oxygen
Correct answer: A
Rationale: Fluorine has the highest electronegativity among the elements listed. Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. Fluorine, being the most electronegative element on the periodic table, has the strongest ability to attract electrons towards itself compared to chlorine, nitrogen, and oxygen. Therefore, fluorine is the correct answer. Chlorine, nitrogen, and oxygen have lower electronegativities compared to fluorine, making them incorrect choices for the element with the highest electronegativity.
3. Here are the solubilities of four substances at 0°C, in grams of solute per 100 mL of water. If the temperature increases to 20°C, what would you expect to happen to the solubility figures?
- A. Citric acid and potassium phosphate will decrease; nitrogen and oxygen will increase.
- B. Citric acid and potassium phosphate will increase; nitrogen and oxygen will decrease.
- C. All four figures will increase.
- D. All four figures will decrease.
Correct answer: C
Rationale: Solubility generally tends to increase with temperature for most solid solutes in liquid solvents due to higher kinetic energy leading to better solute-solvent interactions. As the temperature increases from 0°C to 20°C, all four solubility figures are expected to increase. Choice A is incorrect because solubility tends to increase with temperature. Choice B is incorrect as well for the same reason. Choice D is incorrect because the solubility of solid solutes typically increases with temperature.
4. What are positively charged ions called?
- A. Neutrons
- B. Protons
- C. Cations
- D. Electrons
Correct answer: C
Rationale: Positively charged ions are called cations. When an atom loses electrons, it becomes positively charged and is referred to as a cation. Neutrons are neutral particles found in the nucleus of an atom, not charged. Protons are positively charged particles in the nucleus. Electrons are negatively charged particles orbiting the nucleus, not positively charged ions.
5. What is the chemical reaction that involves breaking down a compound into component parts?
- A. Decomposition
- B. Synthesis
- C. Combustion
- D. Single replacement
Correct answer: A
Rationale: Decomposition is the correct answer because in a decomposition reaction, a compound is broken down into simpler substances. This type of reaction involves the splitting of a compound into its component parts, often through the use of heat, light, or electricity. Synthesis (choice B) is the opposite process where simpler substances are combined to form a more complex compound. Combustion (choice C) is a reaction involving rapid oxidation often accompanied by heat and light. Single replacement (choice D) is a reaction where one element replaces another in a compound.
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