Chemistry

Chemistry Related

Review Chemistry related questions and content

Which of the following reactions is a decomposition reaction?
1. 2H2 + O2 → 2H2O
2. 2Na + Cl2 → 2NaCl
3. CaCO3 → CaO + CO2
4. PbCO3(s) → PbO(s) + CO2(g)

  • A. 1
  • B. 2 and 3
  • C. 4
  • D. All of them are decomposition reactions.
Correct Answer: C

Rationale: A decomposition reaction involves a single compound breaking down into simpler substances. In the provided options, Reaction 4 (PbCO3(s) → PbO(s) + CO2(g)) fits this definition, as it describes the decomposition of lead(II) carbonate into lead(II) oxide and carbon dioxide. Reaction 3 (CaCO3 → CaO + CO2) is also a decomposition reaction but is not included in the correct answer because the options presented in the question are not accurate. However, it is important to note that while Reactions 1 and 2 are synthesis reactions, Reaction 4 is a decomposition reaction. Therefore, the correct answer is option C, indicating that Reaction 4 is a decomposition reaction

You may also like to solve these questions

Arrange the following unknown fluids in the correct order of how they would separate in a beaker, listed from bottom to top, based on the given measurements.

  • A. A, B, C
  • B. A, C, B
  • C. C, A, B
  • D. B, A, C
Correct Answer: B

Rationale: To determine the order of separation in a beaker, we need to consider the densities of the fluids. Density (d) = mass (m) / volume (V). Comparing the densities of the fluids, we find: Fluid A: d = 2060g / 2000mL = 1.03 g/mL, Fluid B: d = 672g / 850mL = 0.79 g/mL, Fluid C: d = 990g / 1100mL = 0.90 g/mL. Since fluids separate in a beaker based on their densities (with the highest density sinking to the bottom), the correct order from bottom to top is B (highest density), then C, and finally A (lowest density). Therefore, the correct answer is A,C,B.

The products of a reaction are CO2 and H2O. Which type of reaction is this most likely to be?

  • A. Synthesis
  • B. Decomposition
  • C. Single replacement
  • D. Combustion
Correct Answer: D

Rationale: The reaction products CO2 and H2O indicate the formation of carbon dioxide and water, which are typical products of a combustion reaction. Combustion reactions involve the rapid combination of a substance with oxygen, producing heat and light energy. In this case, the presence of CO2 and H2O suggests a combustion reaction where a hydrocarbon or organic compound has reacted with oxygen to form these products. Therefore, the correct answer is 'Combustion' (choice D) as it aligns with the formation of CO2 and H2O in this reaction scenario.

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.

What is the charge on potassium in the compound KCl?

  • A. -1
  • B. +1
  • C. -2
  • D. +2
Correct Answer: B

Rationale: In the compound KCl, the overall charge must be zero since it is a neutral compound. Chlorine (Cl) typically has a charge of -1 in ionic compounds. Therefore, for the compound to be neutral, potassium (K) must have a charge of +1 to balance the -1 charge of chlorine. This results in a total charge of 0 for the compound. Thus, the correct answer is +1. The positively charged potassium ion (K+) combines with the negatively charged chloride ion (Cl-) to form an electrically neutral compound, potassium chloride (KCl).

What type of reaction is represented by the equation KCl → K + Cl₂?

  • A. Synthesis
  • B. Decomposition
  • C. Single replacement
  • D. Double replacement
Correct Answer: B

Rationale: The reaction KCl → K + Cl2 is an example of a decomposition reaction. In a decomposition reaction, a compound breaks down into its constituent elements or simpler compounds. In this case, potassium chloride (KCl) decomposes into potassium (K) and chlorine gas (Cl2). Therefore, the correct answer is B, Decomposition.

Copyright © 2025 Nokea. All rights reserved.