HESI A2
HESI A2 Chemistry Practice Test
1. What is a balanced equation?
- A. A description where reactants and products are not equal
- B. An equation where the number of each type of atom is the same on both sides
- C. A chemical formula showing only reactants
- D. An equation without coefficients
Correct answer: B
Rationale: A balanced equation is one where the number of each type of atom is the same on both sides, fulfilling the law of conservation of mass. This principle ensures that the total number of atoms of each element is equal in both reactants and products, signifying that no atoms are created or destroyed, but rather rearranged. Choice A is incorrect because a balanced equation has equal numbers of atoms in the reactants and products. Choice C is incorrect as a balanced equation includes both reactants and products. Choice D is incorrect because coefficients are essential in balancing equations by adjusting the number of atoms present.
2. What is the correct name of AgNO₃?
- A. Argent nitrous
- B. Argent oxide
- C. Silver nitrite
- D. Silver nitrate
Correct answer: D
Rationale: The correct name for AgNO₃ is silver nitrate. In chemical nomenclature, the element symbol Ag represents silver, and the polyatomic ion NO₃ is known as nitrate. Therefore, when the silver ion (Ag⁺) combines with the nitrate ion (NO₃⁻), the resulting compound is named silver nitrate (AgNO₃). Choices A, B, and C are incorrect because they do not accurately represent the composition of AgNO₃. Argent nitrous (Choice A) and Argent oxide (Choice B) do not reflect the correct anion, and Silver nitrite (Choice C) uses a different anion altogether.
3. What are mixtures of 2 or more metals called?
- A. Solutions
- B. Alloys
- C. Compounds
- D. Suspensions
Correct answer: B
Rationale: Alloys are mixtures of two or more metals, combining their properties to create materials with enhanced characteristics. Examples of alloys include bronze (copper and tin) and steel (iron and carbon). Alloys are commonly used in various industries due to their improved strength, durability, and other desirable qualities. Solutions (Choice A) refer to a homogeneous mixture of two or more substances, where one substance is dissolved in another. Compounds (Choice C) are substances composed of two or more elements chemically combined in fixed proportions. Suspensions (Choice D) are heterogeneous mixtures where particles are dispersed but can settle out over time.
4. What term is used to describe the emission of particles from an unstable nucleus?
- A. Radioactivity
- B. Radiation
- C. Decay
- D. Fusion
Correct answer: A
Rationale: Radioactivity is the term used to describe the emission of particles from an unstable nucleus. When a nucleus is unstable, it undergoes radioactive decay by emitting particles such as alpha or beta particles. This process releases energy and transforms the unstable nucleus into a more stable configuration. Choice B, 'Radiation,' is a broad term that encompasses various forms of energy emitted from a source; it is not specific to the emission from an unstable nucleus. Choice C, 'Decay,' is closely related but doesn't specifically indicate the emission of particles from an unstable nucleus. Choice D, 'Fusion,' refers to the process of combining nuclei to form a heavier nucleus, not the emission of particles from an unstable nucleus.
5. Which of the following elements is the most electronegative?
- A. Oxygen
- B. Fluorine
- C. Nitrogen
- D. Sodium
Correct answer: B
Rationale: Fluorine is the most electronegative element on the periodic table. It has the highest electronegativity value, indicating its strong ability to attract electrons in a chemical bond. This property makes it highly reactive, explaining why it is the correct answer in this question. Oxygen and Nitrogen are also electronegative elements, but they are not as electronegative as Fluorine. Sodium, on the other hand, is not electronegative; it is an electropositive element.
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