which of these factors would not affect rates of reaction

HESI A2

Chemistry HESI A2 Practice Test

1. Which of the following factors would not affect rates of reaction?

A. Temperature
B. Surface area
C. Pressure
D. Time

Correct answer: D

Rationale: Time would not directly affect rates of reaction. The rate of a chemical reaction is determined by factors that affect the frequency of successful collisions between reactant molecules, leading to a reaction. Temperature, surface area, and pressure can influence reaction rates by impacting the kinetic energy of molecules, the exposed surface for collisions, and the concentration of reactants, respectively. However, time, in the context of this question, does not alter the rate of reaction but may affect the extent of the reaction or the amount of product formed over time.

2. What type of chemical reaction is represented by AB → A + B?

A. Synthesis
B. Decomposition
C. Single replacement
D. Double replacement

Correct answer: B

Rationale: The chemical equation AB → A + B represents a decomposition reaction. In a decomposition reaction, a single compound breaks down into two or more simpler substances. In this specific reaction, compound AB is decomposed into its elements, A and B, making it a decomposition reaction. Choice A, Synthesis, involves the combination of two or more substances to form a more complex product, which is not the case here. Choices C and D, Single replacement and Double replacement, involve the exchange of ions between compounds or elements, which is not happening in the given reaction.

3. What statement about global warming is made in the passage on the Amazon Rainforest?

A. Global warming is caused by deforestation.
B. Global warming is unrelated to deforestation.
C. Global warming is exaggerated.
D. Global warming is not a concern.

Correct answer: A

Rationale: The correct statement about global warming in the passage on the Amazon Rainforest is that it is caused by deforestation. The passage explains that cutting down trees in the rainforest increases the amount of carbon dioxide in the air, leading to global warming. This is supported by the fact that the burning of Brazilian rainforests alone produces 200 million metric tons of carbon dioxide a year. Choice B is incorrect as the passage clearly establishes a direct link between deforestation and global warming. Choice C is incorrect as the passage does not suggest that global warming is exaggerated, but rather highlights the harmful effects of deforestation. Choice D is incorrect as the passage emphasizes the serious concern of global warming due to deforestation.

4. A chemist takes 100 mL of a 40 g NaCl solution and dilutes it to 1L. What is the concentration (molarity) of the new solution?

A. 0.04 M NaCl
B. 0.25 M NaCl
C. 0.40 M NaCl
D. 2.5 M NaCl

Correct answer: C

Rationale: Initially, the chemist has 40 g of NaCl in 100 mL of solution. To find the initial molarity, we need to calculate the number of moles of NaCl using the molar mass of NaCl (58.44 g/mol). After dilution to 1 L, the molarity of the new solution can be calculated by dividing the moles of NaCl by the total volume in liters. Therefore, the concentration (molarity) of the new solution is 0.40 M NaCl. Choice A (0.04 M NaCl) is incorrect because it doesn't consider the correct molar concentration after dilution. Choice B (0.25 M NaCl) is incorrect as it also doesn't account for the correct molar concentration post-dilution. Choice D (2.5 M NaCl) is incorrect as it is too concentrated given the initial amount of NaCl and the dilution factor.

5. Compare: 0.045 is _____ to 0.054.

A. Greater than
B. Less than
C. Less than or equal to
D. Equal

Correct answer: B

Rationale: The correct answer is B. When comparing 0.045 and 0.054, 0.045 is less than 0.054. Therefore, the correct relation is 'Less than.' Choice A ('Greater than') is incorrect because 0.045 is not greater than 0.054. Choice C ('Less than or equal to') is incorrect because 0.045 is strictly less than 0.054, not less than or equal to. Choice D ('Equal') is incorrect because 0.045 and 0.054 are not equal.