HESI A2
HESI A2 Chemistry Questions
1. What is the name of the process by which a gas turns into a liquid?
- A. Sublimation
- B. Condensation
- C. Evaporation
- D. Deposition
Correct answer: B
Rationale: The correct answer is B: Condensation. Condensation is the process where gas transforms into a liquid. When gas cools down, it loses energy and its particles come closer, leading to the formation of liquid droplets. Sublimation is the direct transition from solid to gas without passing through the liquid state. Evaporation is the process of liquid turning into a gas, and deposition is the transition of gas directly into a solid. Therefore, choices A, C, and D are incorrect as they describe different phase transitions.
2. 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.
3. Which substance is a product of photosynthesis?
- A. Carbon dioxide
- B. Oxygen
- C. Water
- D. Glucose
Correct answer: D
Rationale: During photosynthesis, plants and other organisms convert carbon dioxide and water into glucose and oxygen. Glucose is a carbohydrate produced by plants as a result of photosynthesis, serving as their main source of energy. Oxygen is released as a byproduct of this process, while carbon dioxide and water are the raw materials used to produce glucose. Therefore, the correct answer is 'Glucose,' making it a vital product of the photosynthesis process. Choices A, B, and C are incorrect as carbon dioxide and water are the reactants needed for photosynthesis, and oxygen is released as a byproduct.
4. What determines polarity in a molecule?
- A. Bond length
- B. Bond strength
- C. Electronegativity
- D. Molecular weight
Correct answer: C
Rationale: Polarity in a molecule is determined by the difference in electronegativity between the atoms forming the bond. The greater the difference in electronegativity, the more polar the bond and molecule become. This difference leads to an uneven distribution of electron density within the bond, creating partial positive and negative charges on the atoms involved. Choices A, B, and D are incorrect. Bond length and strength do not determine polarity, and molecular weight is not directly related to the polarity of a molecule.
5. Which of these intermolecular forces might represent attraction between atoms of a noble gas?
- A. Dipole-dipole interaction
- B. London dispersion force
- C. Keesom interaction
- D. Hydrogen bonding
Correct answer: B
Rationale: Noble gases are non-polar molecules without a permanent dipole moment. The only intermolecular force applicable to noble gases is the London dispersion force, also known as Van der Waals forces. This force is a temporary attractive force resulting from the formation of temporary dipoles in non-polar molecules. Dipole-dipole interactions, Keesom interactions, and hydrogen bonding involve significant dipoles or hydrogen atoms bonded to electronegative atoms, which do not apply to noble gases.
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