HESI A2
HESI A2 Chemistry Questions
1. Which element is a metalloid?
- A. Silicon
- B. Lead
- C. Helium
- D. Aluminum
Correct answer: A
Rationale: The correct answer is 'Silicon.' Silicon is a metalloid, which means it has properties of both metals and nonmetals. It is commonly used in electronic devices due to its semiconductor properties. Lead (Choice B) is a metal, Helium (Choice C) is a noble gas, and Aluminum (Choice D) is a metal.
2. Which of the following is a characteristic of an exothermic reaction?
- A. It absorbs heat
- B. It releases heat
- C. It remains neutral
- D. It requires energy input
Correct answer: B
Rationale: An exothermic reaction is characterized by the release of heat. During an exothermic reaction, energy is released in the form of heat to the surroundings, resulting in a temperature increase. This distinguishes it from endothermic reactions, which absorb heat from the surroundings. Choice A is incorrect because exothermic reactions do not absorb heat; instead, they release heat. Choice C is incorrect as exothermic reactions do not remain neutral; they involve a net release of energy. Choice D is incorrect as exothermic reactions do not require energy input; instead, they release energy.
3. What charge do Group IA elements have?
- A. +1
- B. +2
- C. +3
- D. 0
Correct answer: A
Rationale: Group IA elements, also known as alkali metals, have a +1 charge. They readily lose one electron to achieve a stable electron configuration, forming ions with a single positive charge. This makes +1 the correct choice. Choices B, C, and D are incorrect because alkali metals in Group IA typically lose one electron, so they do not have a +2, +3, or 0 charge.
4. 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.
5. What is the energy required to remove the outermost electron from an atom called?
- A. covalent bonding
- B. electronegativity
- C. atomic radius
- D. ionization energy
Correct answer: D
Rationale: Ionization energy is the energy needed to remove the outermost electron from an atom, resulting in the formation of a positively charged ion. The higher the ionization energy, the more difficult it is to extract an electron. Electronegativity, however, measures an atom's ability to attract shared electrons in a chemical bond. Atomic radius refers to the distance from the nucleus to the outermost electron. Covalent bonding involves sharing electron pairs between atoms to create a stable bond. Therefore, the correct answer is ionization energy as it specifically relates to the energy needed to remove an electron from an atom.
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