Nokea
The chemical equation Cr + Fe(NO₃)₂ → Fe + Cr(NO₃)₂ is an example of which type of reaction?
- A. Single replacement
- B. Decomposition
- C. Double replacement
- D. Combustion
Correct Answer: A
Rationale: The correct answer is A: Single replacement. In this reaction, chromium (Cr) replaces iron (Fe) in the compound Fe(NO₃)₂, resulting in the formation of Fe and Cr(NO₃)₂. Single replacement reactions involve an element and a compound, where the element replaces another element in the compound. The general form of a single replacement reaction is A + BC → AC + B, where A is an element and BC is a compound. This type of reaction is also known as a displacement reaction, where a more reactive element displaces a less reactive element in a compound.
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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.
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.
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.
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.
Which of the following statements about dissociation is false?
- A. It is reversible.
- B. Ions are not present.
- C. It involves molecules separating.
- D. None of the above.
Correct Answer: B
Rationale: The correct answer is B - 'Ions are not present.' Dissociation involves the separation of molecules into ions. It is a reversible process where molecules break apart into ions. Choice A is true as dissociation is reversible, and Choice C is accurate as it correctly describes the process of dissociation. Therefore, the false statement is that ions are not present during dissociation.