HESI A2
Chemistry HESI A2 Quizlet
1. What is the charge of noble gases?
- A. -1
- B. 0
- C. 1
- D. 2
Correct answer: B
Rationale: The correct answer is B: 0. Noble gases have a charge of 0 because they have full valence shells and are inert. This makes them stable and unreactive, resulting in a charge of 0 as they do not readily gain or lose electrons. Choices A, C, and D are incorrect because noble gases do not typically form ions by gaining or losing electrons, so they do not carry a charge of -1, 1, or 2.
2. 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.
3. What are the products of the combustion of a hydrocarbon?
- A. Water and carbon dioxide
- B. Water and oxygen
- C. Hydrogen and carbon monoxide
- D. Carbon dioxide and oxygen
Correct answer: A
Rationale: When a hydrocarbon undergoes combustion, it reacts with oxygen to produce water and carbon dioxide as the main products. The general chemical equation for the combustion of a hydrocarbon is hydrocarbon + oxygen → carbon dioxide + water. Therefore, the correct answer is 'Water and carbon dioxide.' Choices B, C, and D are incorrect because water and carbon dioxide are the primary products of hydrocarbon combustion, not water and oxygen, hydrogen and carbon monoxide, or carbon dioxide and oxygen.
4. What is the process of breaking bonds and forming new bonds to create new chemical compounds?
- A. Physical reaction
- B. Chemical reaction
- C. Nuclear reaction
- D. Mechanical reaction
Correct answer: B
Rationale: A chemical reaction involves the breaking and forming of bonds to create new substances. During a chemical reaction, the original chemical bonds are broken, and new bonds are formed to produce one or more new substances with different properties from the reactants. This transformation is a fundamental concept in chemistry and distinguishes chemical reactions from physical, nuclear, or mechanical reactions. Choice A, 'Physical reaction,' does not involve the breaking and forming of chemical bonds but rather changes in physical state or appearance. Choice C, 'Nuclear reaction,' involves changes in the nuclei of atoms, not the breaking and forming of chemical bonds. Choice D, 'Mechanical reaction,' refers to reactions involving physical forces or movements, not the breaking and forming of chemical bonds as in a chemical reaction.
5. What is a mole?
- A. 6.02 x 10^23
- B. 1.00 x 10^24
- C. 6.02 x 10^22
- D. 6.02 x 10^25
Correct answer: A
Rationale: A mole is a unit used in chemistry to represent Avogadro's number, which is approximately 6.02 x 10^23. This number corresponds to the number of particles (atoms, molecules, ions) in one mole of a substance. Choice A, 6.02 x 10^23, is the correct answer as it accurately defines a mole. Choices B, C, and D provide values that are not equivalent to Avogadro's number, making them incorrect answers.
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