Nokea
What is 119°K in degrees Celsius?
- A. 32°C
- B. -154°C
- C. 154°C
- D. -32°C
Correct Answer: B
Rationale: The correct answer is 'B: -154°C.' To convert Kelvin to Celsius, you subtract 273.15 from the temperature in Kelvin. For 119°K: 119 - 273.15 = -154.15. Thus, 119°K is equal to approximately -154°C.
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Chemical reactions in living systems proceed along catabolic pathways, leading to an increase in which of the following?
- A. Entropy
- B. Enthalpy
- C. Glucose
- D. Glycogen
Correct Answer: A
Rationale: In catabolic pathways, complex molecules are broken down into simpler ones, releasing energy. This process increases entropy, which is a measure of disorder or randomness in a system. As molecules are broken down, they become more disordered, causing an increase in entropy. Therefore, the correct answer is 'Entropy.' Enthalpy refers to the total heat content of a system, glucose and glycogen are specific molecules and not directly related to the increase in disorder during catabolic reactions.
Which type of RNA is used to carry the genetic code copied from DNA?
- A. mRNA
- B. tRNA
- C. rRNA
- D. None of the above
Correct Answer: A
Rationale: The correct answer is mRNA (messenger RNA). mRNA is responsible for carrying the genetic information copied from DNA in the cell nucleus to the ribosomes in the cytoplasm where protein synthesis occurs. This process is known as transcription. mRNA acts as a messenger, delivering the genetic instructions to the ribosomes for protein synthesis. In contrast, tRNA (transfer RNA) brings specific amino acids to the ribosome during translation, helping to assemble the protein chain. rRNA (ribosomal RNA) forms a structural and catalytic part of the ribosome itself, aiding in protein synthesis. Therefore, among the options provided, mRNA is the RNA type directly involved in carrying the genetic code from DNA for protein production.
What are van der Waals forces?
- A. the weak forces of attraction between two molecules
- B. the strong forces of attraction between two molecules
- C. hydrogen bonds
- D. conjugal bonds
Correct Answer: A
Rationale: Van der Waals forces are weak intermolecular forces that occur between non-polar molecules. These forces result from temporary fluctuations in electron distribution within the molecules, leading to slight positive and negative charges. This results in weak attraction between molecules through van der Waals forces. Hydrogen bonds, in contrast, are stronger intermolecular forces that specifically occur between molecules containing hydrogen bonded to a highly electronegative atom like oxygen or nitrogen. Conjugal bonds do not exist in chemistry and are not relevant to intermolecular forces.
What products are formed when methane undergoes combustion?
- A. CHâ‚„ and Oâ‚‚
- B. COâ‚‚ and Hâ‚‚O
- C. Both COâ‚‚ and Hâ‚‚O
- D. None of the above
Correct Answer: B
Rationale: When methane (CH₄) undergoes combustion with oxygen (O₂), the products formed are carbon dioxide (CO₂) and water (H₂O). The balanced chemical equation for this reaction is: CH₄ + 2O₂ → CO₂ + 2H₂O. Therefore, the correct answer is option B, CO₂ and H₂O. The combustion of methane is a common example of a hydrocarbon reacting with oxygen to produce carbon dioxide and water, releasing energy in the form of heat and light.
Which material has the smallest specific heat capacity?
- A. water
- B. wood
- C. aluminum
- D. glass
Correct Answer: C
Rationale: Specific heat capacity refers to the amount of heat energy needed to raise the temperature of a substance by a certain amount. In this context, aluminum has the smallest specific heat capacity among the materials listed. This means that aluminum requires the least amount of heat energy to increase its temperature compared to water, wood, and glass. As a result, aluminum is the material with the smallest specific heat capacity in this scenario.