Nokea
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.
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Which type of reaction is exemplified by the chemical equation Cr + Fe(NOÄ‚�)Ä‚‚ Ć’ Fe + Cr(NOÄ‚�)Ä‚�?
- A. Single replacement
- B. Decomposition
- C. Double replacement
- D. Combustion
Correct Answer: A
Rationale: The given chemical equation represents a single replacement reaction. In this type of reaction, one element displaces another element in a compound. In the provided equation, chromium (Cr) replaces iron (Fe) in the compound Fe(NOÄ‚�)Ä‚‚, resulting in the formation of Fe and Cr(NOÄ‚�)Ä‚�. Single replacement reactions involve the substitution of one element for another in a compound, which is precisely demonstrated in this scenario. Therefore, the correct classification for this reaction is a single replacement reaction.
Which type of bond involves sharing pairs of electrons?
- A. Ionic
- B. Covalent
- C. Both
- D. None of the above
Correct Answer: B
Rationale: In a covalent bond, atoms share pairs of electrons to achieve a stable electron configuration. This sharing of electrons leads to the formation of a strong bond between atoms. Ionic bonds, on the other hand, involve the transfer of electrons from one atom to another. Therefore, the correct answer is option B, Covalent, as it specifically describes the sharing of electron pairs, distinguishing it from ionic bonds where electron transfer occurs rather than electron sharing.
What is the term for the reactant that is entirely consumed in a reaction?
- A. limiting reactant
- B. reducing agent
- C. reaction intermediate
- D. reagent
Correct Answer: A
Rationale: The term for the reactant that is entirely consumed in a reaction is the limiting reactant. The limiting reactant is crucial in determining the maximum amount of product that can be formed as it is fully consumed in the reaction. The other choices, reducing agent, reaction intermediate, and reagent, do not specifically refer to the reactant that is completely consumed during the reaction process. Identifying the limiting reactant is essential for calculating the theoretical yield of a reaction and understanding the stoichiometry of the reaction.
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.
An atom of oxygen has more electrons than a neutral oxygen atom. What is this called?
- A. Isotope
- B. Ion
- C. Both are correct
- D. None of the above
Correct Answer: B
Rationale: The correct answer is 'B: Ion.' An ion is formed when an atom gains or loses electrons, resulting in a net positive or negative charge. In this case, an oxygen atom with more electrons than the usual number is referred to as an oxygen ion. Isotopes, on the other hand, are atoms of the same element with different numbers of neutrons. Therefore, an atom of oxygen having more electrons than a neutral oxygen atom is best described as an ion, not an isotope.