HESI A2
HESI A2 Chemistry Questions
1. Which element has the highest electronegativity?
- A. Fluorine
- B. Chlorine
- C. Nitrogen
- D. Oxygen
Correct answer: A
Rationale: Fluorine has the highest electronegativity among the elements listed. Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. Fluorine, being the most electronegative element on the periodic table, has the strongest ability to attract electrons towards itself compared to chlorine, nitrogen, and oxygen. Therefore, fluorine is the correct answer. Chlorine, nitrogen, and oxygen have lower electronegativities compared to fluorine, making them incorrect choices for the element with the highest electronegativity.
2. Which two functional groups would you expect an amino acid to contain?
- A. R-NH2 and R-COOH
- B. R-CHO and R-CO-NH
- C. R-OH and R-COOR
- D. R-O-R and R-COOH
Correct answer: A
Rationale: Amino acids are organic compounds that are characterized by the presence of an amino group (NH2) and a carboxylic acid group (COOH) in their chemical structure. These two functional groups, found in option A, are fundamental components of amino acids and play crucial roles in their classification and biological functions. Option B contains an aldehyde group (CHO) and an amide group (CO-NH), which are not characteristic functional groups of amino acids. Option C includes a hydroxyl group (OH) and an ester group (COOR), which are not typically present in amino acids. Option D presents ether (R-O-R) and carboxylic acid (COOH) functional groups, which do not represent the functional groups commonly found in amino acids.
3. What is a pentose sugar?
- A. A 6 carbon sugar
- B. A 4 carbon sugar
- C. A 5 carbon sugar
- D. A 7 carbon sugar
Correct answer: C
Rationale: A pentose is a 5-carbon sugar, as the prefix 'pent-' signifies five. Therefore, a pentose sugar consists of five carbon atoms. Choice A, 'A 6 carbon sugar,' is incorrect as a pentose sugar specifically has five carbons. Choice B, 'A 4 carbon sugar,' is incorrect as it describes a tetrose sugar, which has four carbons. Choice D, 'A 7 carbon sugar,' is incorrect as it does not correspond to the definition of a pentose sugar.
4. Balance this equation: Fe + Cl2 → FeCl3
- A. 2Fe + 2Cl2 → 2FeCl3
- B. 2Fe + 3Cl2 → 2FeCl3
- C. 3Fe + 2Cl2 → 3FeCl3
- D. 3Fe + 3Cl2 → 6FeCl3
Correct answer: B
Rationale: In the given equation, Fe combines with Cl to form FeCl3. To balance the equation, we need to have the same number of each element on both sides. Since Cl is represented as Cl2 in the equation, we need 3 Cl2 molecules to balance Fe, resulting in 2Fe + 3Cl2 → 2FeCl3. Choice A is incorrect because it only balances Fe but not Cl2. Choice C is incorrect as it balances Fe but not Cl2. Choice D is incorrect as it balances Fe but overbalances Cl2.
5. Which substance forms hydroxide ions when placed in water?
- A. Lemon juice
- B. Battery acid
- C. Vinegar
- D. Lye
Correct answer: D
Rationale: The correct answer is D, lye. Lye, also known as sodium hydroxide (NaOH), is a strong base that forms hydroxide ions (OH-) when placed in water. When lye dissolves in water, it dissociates into sodium ions (Na+) and hydroxide ions, making it an alkaline substance. Lemon juice, battery acid, and vinegar do not form hydroxide ions when placed in water. Lemon juice contains citric acid, battery acid contains sulfuric acid, and vinegar contains acetic acid, none of which produce hydroxide ions when dissolved in water.
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