HESI A2
HESI A2 Chemistry Practice Questions
1. On the periodic table, families of elements with similar properties appear in the same _________.
- A. row
- B. principal energy level
- C. period
- D. column
Correct answer: D
Rationale: Families of elements with similar properties appear in the same column on the periodic table. Columns are also known as groups, and elements within the same group have similar chemical and physical properties due to their identical number of valence electrons. Therefore, the correct answer is 'column.' Choice A, 'row,' is incorrect because rows on the periodic table are called periods, not families or groups of elements. Choice B, 'principal energy level,' is incorrect as it refers to the energy levels of electrons around the nucleus of an atom, not the arrangement of elements with similar properties on the periodic table. Choice C, 'period,' is incorrect as periods represent horizontal rows on the periodic table, where elements do not necessarily have similar properties compared to elements in the same column.
2. Which factor does not affect the reaction rate of a chemical reaction?
- A. Temperature
- B. Surface area
- C. Concentration of reactants
- D. Color of the reactants
Correct answer: D
Rationale: The color of reactants is not a factor that affects the rate of a chemical reaction. Temperature, surface area, and concentration of reactants are known factors that influence the reaction rate. Temperature plays a significant role in altering the reaction rate by affecting the kinetic energy of molecules. Surface area impacts the rate by providing more area for collisions to occur. Concentration affects the frequency of effective collisions. On the other hand, the color of reactants is a physical property that does not directly affect the speed of a chemical reaction.
3. Beta radiation is the product of the decomposition of which particle?
- A. Proton
- B. Neutron
- C. Electron
- D. Photon
Correct answer: B
Rationale: Beta radiation is the result of the decomposition of a neutron. During beta decay, a neutron in an atom's nucleus is transformed into a proton, an electron (beta particle), and an antineutrino. Therefore, the correct answer is 'Neutron.' Choice A, 'Proton,' is incorrect because beta decay does not involve the decomposition of a proton. Choice C, 'Electron,' is incorrect because electrons are actually produced during beta decay. Choice D, 'Photon,' is incorrect as beta radiation does not involve the decomposition of photons.
4. To the nearest whole number, what is the mass of one mole of sodium chloride?
- A. 36 g/mol
- B. 43 g/mol
- C. 58 g/mol
- D. 72 g/mol
Correct answer: C
Rationale: The molar mass of sodium chloride (NaCl) is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl). The atomic mass of sodium is approximately 23 g/mol and chlorine is approximately 35.5 g/mol. Adding these two atomic masses gives us a molar mass of approximately 58 g/mol for sodium chloride (NaCl). Therefore, the correct answer is C, 58 g/mol. Choice A (36 g/mol) is incorrect as it does not account for the individual atomic masses of sodium and chlorine. Choice B (43 g/mol) and choice D (72 g/mol) are also incorrect as they do not reflect the accurate molar mass of sodium chloride.
5. 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.
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