Nokea
Which of the following exhibits the most molecular interactions?
- A. Solid
- B. Liquid
- C. Gas
- D. None of the above
Correct Answer: A
Rationale: The correct answer is 'Solid.' In solids, molecules are closely packed, leading to strong intermolecular forces and the highest number of molecular interactions among the given options. This close proximity results in strong attractions between molecules, creating a high number of interactions. In contrast, liquids have weaker intermolecular forces due to more freedom of movement among molecules, leading to fewer interactions compared to solids. Gases have the least molecular interactions as their molecules are widely dispersed and have minimal attraction to each other, resulting in the lowest number of interactions.
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What is the density of iron if 28.5g of iron is added to a graduated cylinder containing 45.5mL of water, causing the water level to rise to the 49.1mL mark?
- A. 0.63 g/mL
- B. 7.92 g/mL
- C. 0.58 g/mL
- D. None of the above.
Correct Answer: B
Rationale: To calculate density, divide mass by volume. First, determine the volume of iron added by subtracting the initial volume of water from the final volume with iron. The volume of iron is calculated as 49.1mL - 45.5mL = 3.6mL. Density of iron is then determined as the mass of iron divided by the volume of iron, which equals 28.5g / 3.6mL = 7.92 g/mL. Therefore, the correct answer is B, 7.92 g/mL.
What role does carbonic acid play in the human body?
- A. Digests food
- B. Kills viruses
- C. Maintains pH of blood
- D. Grows hair
Correct Answer: C
Rationale: In the human body, carbonic acid, formed when carbon dioxide dissolves in water, plays a crucial role in maintaining the pH balance of blood. It acts as a buffer system, responsible for regulating blood acidity levels and preventing significant pH fluctuations that could harm the body. Choices A, B, and D are inaccurate as they do not reflect the actual function of carbonic acid in the human body.
What distinguishes the 20 common amino acids from each other?
- A. Color
- B. Size
- C. R-group
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C: R-group. The 20 common amino acids share a common backbone structure, but what differentiates them from each other is the side chain or R-group attached to this backbone. The R-group varies in composition and properties among the different amino acids, influencing their overall characteristics and functions. Options A and B are not the primary distinguishing factors among amino acids. Option D is incorrect as the R-group is the key feature that sets apart the 20 common amino acids, contributing to their individual identities and roles in biological processes.
What is the density of a piece of cork with a volume of 23.5 cm³ and a mass of 5.7g?
- A. 0.243g/cm³
- B. 4.123g/cm³
- C. 133.95g/cm³
- D. None of the above
Correct Answer: A
Rationale: Density is calculated by dividing the mass of an object by its volume. In this case, the density of the cork can be calculated by dividing 5.7g by 23.5 cm³, resulting in a density of approximately 0.243g/cm³. Therefore, choice A, 0.243g/cm³, is the correct answer as it accurately represents the density of the cork based on the provided values.
What is the density of carbon tetrachloride if a flask weighing 345.8 g is filled with 225 mL of the liquid, and the total weight of the flask and liquid is 703.55 g?
- A. 1.59 g/mL
- B. 2.76 g/mL
- C. 1.4 g/mL
- D. None of the above
Correct Answer: A
Rationale: To find the density of carbon tetrachloride, we first need to determine the weight of the liquid only. The weight of the liquid can be calculated by subtracting the weight of the empty flask from the total weight of the flask and liquid: 703.55 g - 345.8 g = 357.75 g. Now, using the volume of the liquid (225 mL) and its weight (357.75 g), we can calculate the density: Density = Mass/Volume = 357.75 g / 225 mL ĉ� 1.59 g/mL. Therefore, the correct answer is A, 1.59 g/mL.