HESI A2
HESI A2 Chemistry Questions
1. What is the chemical symbol for sodium?
- A. N
- B. Na
- C. Cl
- D. H
Correct answer: B
Rationale: The correct chemical symbol for sodium is 'Na.' In the periodic table, sodium is represented by the symbol 'Na,' derived from its Latin name 'natrium.' The symbol 'N' represents nitrogen, not sodium. 'Cl' is the symbol for chlorine, and 'H' is the symbol for hydrogen. Therefore, 'Na' is the correct chemical symbol for sodium.
2. What is a benefit of water's ability to make hydrogen bonds?
- A. Lack of cohesiveness
- B. Low surface tension
- C. Use as a nonpolar solvent
- D. High specific heat
Correct answer: D
Rationale: The correct answer is D, high specific heat. Water's ability to form hydrogen bonds results in a high specific heat capacity, allowing it to absorb and release a large amount of heat energy with minimal temperature change. This property is essential for moderating temperature changes in organisms and maintaining stable environmental conditions for life processes. Choices A, lack of cohesiveness, and C, use as a nonpolar solvent, are incorrect. Water actually has high cohesiveness due to its ability to form hydrogen bonds, and it is a polar solvent, not nonpolar. Choice B, low surface tension, is also incorrect as water's hydrogen bonding contributes to its relatively high surface tension.
3. What is the mass number of an atom with 6 protons, 6 neutrons, and 6 electrons?
- A. 12
- B. 18
- C. 6
- D. 8
Correct answer: A
Rationale: The mass number of an atom is the sum of protons and neutrons. In this case, the atom has 6 protons and 6 neutrons, thus the mass number is 6 + 6 = 12. Therefore, choice A (12) is the correct answer. Choices B (18), C (6), and D (8) are incorrect because the mass number is determined by the sum of protons and neutrons, not the number of electrons or a different combination of particles.
4. Which type of change occurs when no change is made to the chemical composition of a substance?
- A. Chemical
- B. Physical
- C. Nuclear
- D. Mechanical
Correct answer: B
Rationale: A physical change refers to alterations in the state of matter without modifying the chemical composition of the substance. Examples of physical changes include changes in state (solid, liquid, gas), shape, size, or phase. In a physical change, the substance may look different or behave differently, but its chemical structure remains the same. On the other hand, chemical changes involve the breaking and forming of chemical bonds, resulting in the creation of entirely new substances with different chemical properties. Nuclear changes involve alterations in the nucleus of an atom, such as radioactive decay. Mechanical changes refer to changes in the position or motion of an object caused by applied forces, like pushing, pulling, or twisting.
5. What are neutral particles called?
- A. Neutrons
- B. Protons
- C. Electrons
- D. Cations
Correct answer: A
Rationale: Neutral particles, which have no electric charge, are known as neutrons. Neutrons are found in the nucleus of an atom along with protons. Electrons carry a negative charge and orbit the nucleus. Cations are positively charged ions formed by losing electrons. Therefore, the correct answer is 'Neutrons' as they are the neutral particles in an atom, unlike protons, electrons, or cations.
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