Nokea
Which compounds are the products of the reaction?
- A. CHâ‚„ and Oâ‚‚
- B. COâ‚‚ and Hâ‚‚O
- C. Both
- D. None of the above
Correct Answer: B
Rationale: The correct answer is 'B: CO₂ and H₂O.' In a combustion reaction between hydrocarbons and oxygen, the products formed are carbon dioxide (CO₂) and water (H₂O). The reaction can be summarized as hydrocarbon + oxygen → carbon dioxide + water. Methane (CH₄) is a hydrocarbon and is not a product of the reaction. Therefore, the correct
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How are chemical equations typically written?
- A. Products → Reactants
- B. Reactants → Products
- C. Reactants + Reactants
- D. Products + Reactants
Correct Answer: B
Rationale: Chemical equations are typically written with reactants listed on the left side of the arrow and products on the right side. This convention signifies the progression of reactants transforming into products during a chemical reaction. Therefore, the correct way chemical equations are typically written is 'Reactants Ć’ Products.'
Which of the following is not an organic compound?
- A. Hâ‚‚O
- B. C₂H₆
- C. C₃H₇O₂
- D. None of the above
Correct Answer: A
Rationale: The correct answer is 'A: H₂O.' An organic compound is defined as a compound that contains carbon and hydrogen atoms bonded together. Choice A, H₂O (water), is composed of hydrogen and oxygen but lacks carbon, making it an inorganic compound. Choices B (C₂H₆) and C (C₃H₇O₂) both contain carbon and hydrogen, thus meeting the criteria for organic compounds. Therefore, the correct answer is A, H₂O, as it does not meet the definition of an organic compound due to the absence of carbon in its structure.
What is the term for the number of protons in an atom?
- A. atomic identity
- B. atomic mass
- C. atomic weight
- D. atomic number
Correct Answer: D
Rationale: The term for the number of protons in an atom is the atomic number. The atomic number is a fundamental property of an element, representing the number of protons in an atom's nucleus. It serves as the unique identity of an element and determines its position on the periodic table and its chemical behavior. Atomic mass refers to the average mass of an atom, including protons, neutrons, and electrons, while atomic weight is the average weight of an element considering the abundance of its isotopes. 'Atomic identity' is not a standard term in chemistry to describe the number of protons in an atom, making option D, 'atomic number,' the correct answer.
A block on your desk acts as a paperweight with measurements of 3 cm by 4 cm by 6 cm. The block has a mass of 184.32 g. What is its density?
- A. 13,271.04 g/cm³
- B. 2.56 g/cm³
- C. 0.39 g/cm³
- D. None of the above
Correct Answer: B
Rationale: Density is calculated by dividing mass by volume. To find the volume of the block, multiply its dimensions (3 cm x 4 cm x 6 cm = 72 cm³). Dividing the mass (184.32 g) by the volume (72 cm³) gives a density of 2.56 g/cm³. Therefore, the correct answer is B.
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.