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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.
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How many hydrogen atoms are present in the reactants?
- A. 2
- B. 4
- C. 1
- D. None of the above
Correct Answer: B
Rationale: To determine the number of hydrogen atoms in the reactants, we need to examine the chemical formula of the reactants. If the formula contains hydrogen atoms, we count them to find the total. In this case, the correct answer is 4 because there are 4 hydrogen atoms present in the reactants. The chemical formula in the reactants indicates the presence of 4 hydrogen atoms. It is crucial to pay close attention to the elements and their quantities in chemical reactions to ensure accurate analysis and understanding of reactants and products.
A flask that weighs 345.8 g is filled with 225 mL of carbon tetrachloride. The weight of the flask and carbon tetrachloride is found to be 703.55 g. From this information, calculate the density of carbon tetrachloride.
- A. 1.59 g/mL
- B. 2.76 g/mL
- C. 1.4 g/mL
- D. None are correct.
Correct Answer: A
Rationale: To find the density of carbon tetrachloride, we need to use the formula Density = Mass / Volume. The mass of carbon tetrachloride can be calculated by subtracting the weight of the empty flask from the weight of the flask filled with carbon tetrachloride: Mass of carbon tetrachloride = 703.55 g - 345.8 g = 357.75 g. Now, we can calculate the density: Density = Mass / Volume = 357.75 g / 225 mL = 1.59 g/mL. Therefore, the correct answer is A, 1.59 g/mL.
Which of the following statements is most accurate regarding the compound 2Hâ‚‚O?
- A. 2Hâ‚‚O has a total of 2 hydrogen atoms.
- B. 2Hâ‚‚O represents two water molecules.
- C. Hâ‚‚O represents two water molecules.
- D. None of the above.
Correct Answer: B
Rationale: The chemical formula 2Hâ‚‚O represents two water molecules. Each water molecule (Hâ‚‚O) consists of 2 hydrogen atoms and 1 oxygen atom. Therefore, 2Hâ‚‚O denotes two separate water molecules, making choice B the correct statement
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.
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.