what is the boiling point of water in c

HESI A2

HESI A2 Chemistry

1. What is the boiling point of water in °C?

A. 90°C
B. 100°C
C. 95°C
D. 80°C

Correct answer: B

Rationale: The correct answer is 100°C. The boiling point of water in Celsius is 100°C, which is standard at sea level. This is the temperature at which water changes from a liquid to a gas phase under standard atmospheric pressure. Choice A (90°C), Choice C (95°C), and Choice D (80°C) are incorrect because they do not represent the standard boiling point of water at sea level.

2. Which type of chemical bond is the strongest?

A. Ionic
B. Hydrogen
C. Covalent
D. Metallic

Correct answer: C

Rationale: Covalent bonds, especially those formed between non-metals, are the strongest type of chemical bond. In covalent bonds, atoms share electrons, creating a strong bond that requires a significant amount of energy to break. Choice A, ionic bonds, are strong but generally weaker than covalent bonds as they involve the transfer of electrons rather than sharing. Choice B, hydrogen bonds, are relatively weak intermolecular forces, not true chemical bonds. Choice D, metallic bonds, are strong but typically not as strong as covalent bonds. Metallic bonds involve a 'sea of electrons' shared between metal atoms, providing strength but with less directional bonding compared to covalent bonds.

3. What is the role of a catalyst in a chemical reaction?

A. Slows down the reaction
B. Has no effect
C. Speeds up the reaction
D. Stops the reaction

Correct answer: C

Rationale: A catalyst speeds up a chemical reaction by lowering the activation energy required for the reaction to occur. It does not get consumed in the reaction and remains unchanged at the end, allowing it to facilitate multiple reaction cycles. Choice A is incorrect because a catalyst actually speeds up the reaction. Choice B is incorrect because catalysts do have an effect by accelerating the reaction. Choice D is incorrect because catalysts do not stop the reaction, but rather increase the reaction rate.

4. Which of these types of intermolecular force is weakest?

A. Dipole-dipole interaction
B. London dispersion force
C. Hydrogen bonding
D. Ionic bonding

Correct answer: B

Rationale: The correct answer is B, London dispersion force. London dispersion forces are the weakest type of intermolecular force among the options provided. These forces arise from temporary fluctuations in electron distribution within molecules, leading to temporary dipoles. London dispersion forces are present in all molecules and are generally weaker than dipole-dipole interactions, hydrogen bonding, and ionic bonding. Dipole-dipole interactions are stronger than London dispersion forces as they involve permanent dipoles in molecules. Hydrogen bonding is stronger than both London dispersion and dipole-dipole interactions as it is a special type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like oxygen or nitrogen. Ionic bonding is the strongest type of intermolecular force among the options, but it is not the correct answer for the weakest type of force.

5. Which best defines the molarity of an aqueous sugar solution?

A. Grams of sugar per milliliter of solution
B. Moles of sugar per milliliter of solution
C. Grams of sugar per liter of solution
D. Moles of sugar per liter of solution

Correct answer: D

Rationale: The molarity of a solution is defined as the number of moles of solute per liter of solvent. In the case of an aqueous sugar solution, the molarity would be expressed as moles of sugar per liter of solution. This is because molarity is a measurement of the concentration of a solute in a solution based on the number of moles present in a given volume of the solution. Therefore, the correct answer is D. Choices A, B, and C are incorrect because the molarity is specifically defined in terms of moles of solute per liter of solution, not in grams per milliliter or grams per liter. Molarity is a unit of concentration that relates the amount of solute to the volume of the solution, not the mass of the solute.