HESI A2
HESI A2 Chemistry
1. Where would you expect tap water to fall on the pH scale?
- A. Between 1 and 3
- B. Between 4 and 6
- C. Between 6 and 8
- D. Between 8 and 10
Correct answer: C
Rationale: Tap water typically falls within the pH range of 6 to 8, making it slightly acidic to neutral. Most municipal water systems aim to provide water that is safe for consumption and falls within this pH range. A pH level of 7 is considered neutral, so tap water may vary slightly on either side of this number but typically remains within the 6 to 8 range to ensure it is safe for consumption. Choices A, B, and D are incorrect because tap water is not expected to have a pH as low as 1-3 (highly acidic) or as high as 8-10 (alkaline); it usually falls within the slightly acidic to neutral range, hence falling between 6 and 8 on the pH scale.
2. What is the name of the compound CH₃-CH₂-CH₂-CH₃?
- A. Cyclobutane
- B. Butane
- C. Butene
- D. Butyne
Correct answer: B
Rationale: The compound CH₃-CH₂-CH₂-CH₃ is named butane. Butane is a straight-chain alkane comprising four carbon atoms connected by single bonds. The prefix 'but-' denotes the presence of four carbon atoms, while the suffix '-ane' indicates it is an alkane with single bonds between the carbon atoms. Choice A, Cyclobutane, is incorrect as it refers to a cyclic hydrocarbon with four carbon atoms in a ring structure. Choice C, Butene, is incorrect because it is an alkene with a double bond between two carbon atoms, not a saturated hydrocarbon like butane. Choice D, Butyne, is also incorrect as it is an alkyne with a triple bond between two carbon atoms, unlike the single bonds in butane.
3. What is the net charge of an ionic compound?
- A. 0
- B. -1
- C. +1
- D. Variable
Correct answer: A
Rationale: The correct answer is A: 0. Ionic compounds have a net charge of 0 because they are formed by the combination of positively charged ions (cations) and negatively charged ions (anions) in a way that neutralizes their charges. This balanced combination results in an electrically neutral compound. Therefore, the net charge of an ionic compound is typically 0. Choices B, C, and D are incorrect because ionic compounds are designed to have a total neutral charge, with the positive charges balancing out the negative charges.
4. 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.
5. What type of bond is an electrostatic attraction between two oppositely charged ions?
- A. Covalent
- B. Metallic
- C. Ionic
- D. Hydrogen
Correct answer: C
Rationale: An ionic bond forms when one atom transfers electrons to another, resulting in the formation of positively and negatively charged ions. The attraction between these oppositely charged ions creates an electrostatic bond, known as an ionic bond. Choice A, covalent bonds, involve the sharing of electrons, not the transfer. Choice B, metallic bonds, occur between metal atoms and involve a 'sea of electrons' that are delocalized. Choice D, hydrogen bonds, are much weaker interactions between hydrogen atoms and other electronegative atoms like oxygen or nitrogen.
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