HESI A2
HESI A2 Chemistry Questions
1. What is the pH of a neutral solution?
- A. 7
- B. 0
- C. 14
- D. 4
Correct answer: A
Rationale: The correct answer is A: 7. A neutral solution has a pH of 7. In the pH scale, values below 7 are acidic, 7 is neutral, and values above 7 are basic. Therefore, a solution with a pH of 7 is considered neutral as it is neither acidic nor basic. Choices B, C, and D are incorrect because a pH of 0 indicates a strong acid, a pH of 14 indicates a strong base, and a pH of 4 indicates an acidic solution. None of these values represent a neutral solution.
2. Which substance shows a decrease in solubility in water with an increase in temperature?
- A. NaCl
- B. O
- C. KI
- D. CaCl
Correct answer: C
Rationale: Potassium iodide (KI) shows a decrease in solubility in water with an increase in temperature. This is due to the dissolution of KI in water being an endothermic process. When the temperature rises, the equilibrium shifts toward the solid state, leading to a decrease in solubility. Therefore, as the temperature increases, KI becomes less soluble in water. Choice A (NaCl) and Choice D (CaCl) do not exhibit a decrease in solubility with an increase in temperature. NaCl and CaCl are generally more soluble in water at higher temperatures. Choice B (Oxygen) is a gas and not typically considered in solubility discussions involving solids or liquids dissolving in water.
3. What form of radiation is composed of electrons traveling at around 16,000 km/sec?
- A. Alpha radiation
- B. Beta radiation
- C. Gamma radiation
- D. Delta radiation
Correct answer: B
Rationale: Beta radiation is composed of high-energy electrons (β- particles) or positrons (β+ particles) traveling at considerable speeds. In this case, the electrons traveling at around 16,000 km/sec align with the characteristics of beta radiation, making it the correct choice. Alpha radiation consists of helium nuclei, gamma radiation is electromagnetic radiation of high frequency, and delta radiation is not a recognized form of radiation, making them all incorrect choices.
4. Which branch of chemistry deals with the quantities and numeric relationships between compounds in a chemical reaction?
- A. Stoichiometry
- B. Molecular chemistry
- C. Atomic chemistry
- D. Thermodynamics
Correct answer: A
Rationale: Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. It involves the calculation of quantities of substances consumed and produced in a chemical reaction based on the balanced chemical equation. Choice B, 'Molecular chemistry,' is incorrect as it focuses on the structure, properties, and reactions of molecules. Choice C, 'Atomic chemistry,' is incorrect as it primarily deals with the study of atoms and their interactions. Choice D, 'Thermodynamics,' is incorrect as it pertains to the study of energy and heat transfer in chemical and physical processes.
5. What is the correct name of MgO?
- A. Manganese oxide
- B. Magnesium oxide
- C. Magnesium oxate
- D. Magnesium hydroxide
Correct answer: B
Rationale: The correct name of MgO is Magnesium oxide. Mg represents the chemical symbol for magnesium, and O represents the chemical symbol for oxygen. When these elements combine, they form magnesium oxide. Option A, Manganese oxide, is incorrect as it refers to a compound of manganese and oxygen, not magnesium. Option C, Magnesium oxate, is not a valid chemical compound name. Option D, Magnesium hydroxide, refers to a different compound consisting of magnesium, oxygen, and hydrogen.
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