Nokea
What is present in an emulsion?
- A. Water and salt
- B. Two or more immiscible liquids
- C. Any liquids
- D. All of the above
Correct Answer: B
Rationale: In an emulsion, two or more immiscible liquids are present. Immiscible liquids are those that do not mix together and form separate layers, such as oil and water. Emulsions are a type of colloid where one liquid is dispersed in another. Water and oil are a common example of an emulsion, where the two liquids do not mix naturally but can be forced to form a stable mixture with the help of an emulsifying agent.
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What is the building block of proteins?
- A. Lipids
- B. Amino acids
- C. DNA
- D. Cells
Correct Answer: B
Rationale: Amino acids are the fundamental building blocks of proteins. Proteins are large biomolecules made up of one or more chains of amino acids. Each amino acid contains an amine group, a carboxylic acid group, and a side chain specific to each amino acid. When amino acids link together through peptide bonds, they form proteins. Lipids are a different type of biomolecule that includes fats, oils, and phospholipids. DNA is a nucleic acid that carries genetic information but is not directly involved in the structure of proteins. Cells are the basic structural and functional units of living organisms, not the building blocks of proteins.
Which of the following describes atomic mass?
- A. Mass of protons and electrons
- B. Mass of neutrons and electrons
- C. Average mass of that element's isotopes
- D. Number of moles in a solution
Correct Answer: C
Rationale: The correct answer is C: Average mass of that element's isotopes. Atomic mass is the weighted average mass of the isotopes of an element, considering the natural abundance of each isotope. It is not just the sum of protons and neutrons or neutrons and electrons. Understanding atomic mass is crucial in chemistry as it helps in determining the molar mass of elements, which is essential in various chemical calculations such as stoichiometry and reaction equations.
Which type of reaction is most likely represented by the products CO2 + H2O: CO2 + H2O?
- A. Synthesis
- B. Decomposition
- C. Single replacement
- D. Combustion
Correct Answer: D
Rationale: The reaction products CO2 and H2O suggest a combustion reaction. In a combustion reaction, a substance reacts with oxygen gas (O2) to produce carbon dioxide (CO2) and water (H2O) as products. The given reaction matches the characteristic products of a combustion reaction, indicating that option D, 'Combustion,' is the correct answer.
Which subatomic particle can always be used to identify an atom?
- A. Protons
- B. Neutrons
- C. Electrons
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Protons. Protons are positively charged subatomic particles found in the nucleus of an atom. The number of protons in an atom's nucleus determines the element's identity. While neutrons and electrons are also essential components of an atom, it is the number of protons that uniquely identifies the element. Therefore, protons can always be used to identify an atom.
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.