Nokea
What is the molarity of a solution containing 45 moles of NaCl in 4 liters?
- A. 0.11 M NaCl
- B. 0.45 M NaCl
- C. 1.8 M NaCl
- D. 8.9 M NaCl
Correct Answer: A
Rationale: To calculate the molarity of a solution, you use the formula: Molarity (M) = moles of solute / liters of solution. In this case, M = 45 moles / 4 L = 11.25 M. The correct answer is 0.11 M NaCl. Choice B is incorrect as it doesn't match the calculated value. Choice C is also incorrect as it is significantly higher than the correct molarity. Choice D is incorrect as it is excessively high compared to the calculated value.
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What is 0 K equal to in °C?
- A. -300°C
- B. -273°C
- C. -250°C
- D. -200°C
Correct Answer: B
Rationale: 0 Kelvin, also known as absolute zero, is equal to -273°C. This is the point at which all molecular motion stops, making it the lowest possible temperature on the Kelvin scale. Choice A (-300°C) is incorrect as it is not the correct conversion of 0 K to °C. Choice C (-250°C) and Choice D (-200°C) are also incorrect as they do not correspond to the accurate conversion of 0 K to °C.
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.
What form of radiation is composed of electrons traveling at around 16,000 km/sec?
- A. Alpha radiation
- B. Beta radiation
- C. Gamma radiation
- D. Delta radiation
Correct Answer: B
Rationale: Beta radiation is composed of high-energy electrons (β- particles) or positrons (β+ particles) traveling at considerable speeds. In this case, the electrons traveling at around 16,000 km/sec align with the characteristics of beta radiation, making it the correct choice. Alpha radiation consists of helium nuclei, gamma radiation is electromagnetic radiation of high frequency, and delta radiation is not a recognized form of radiation, making them all incorrect choices.
What is the correct formula for potassium chloride?
- A. NaCl
- B. KCl
- C. KCl
- D. ClK
Correct Answer: B
Rationale: The correct formula for potassium chloride is KCl. In chemical formulas, the symbol for the cation (positive ion) comes first followed by the symbol for the anion (negative ion). Potassium is represented by the symbol K, while chloride is represented by the symbol Cl. Therefore, the formula for potassium chloride is KCl. Choice A (NaCl) is the formula for sodium chloride, not potassium chloride. Choice C is a duplicate of choice B, and choice D (ClK) is an incorrect arrangement of the symbols for potassium and chloride.
The three important allotropic forms of phosphorus are red, white, and ___________.
- A. green
- B. gray
- C. black
- D. silver
Correct Answer: C
Rationale: The three important allotropic forms of phosphorus are red, white, and black. These forms indicate the different physical properties and reactivity of phosphorus under various conditions. Red phosphorus is more stable and less reactive than white phosphorus, while black phosphorus is the least reactive form. Choice C, 'black,' is the correct answer as it completes the sequence of allotropic forms of phosphorus. Choices A, 'green,' B, 'gray,' and D, 'silver,' are incorrect as they do not represent recognized forms of phosphorus.