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What is the density of a piece of cork with a volume of 23.5 cm³ and a mass of 5.7g?
- A. 0.243g/cm³
- B. 4.123g/cm³
- C. 133.95g/cm³
- D. None of the above
Correct Answer: A
Rationale: Density is calculated by dividing the mass of an object by its volume. In this case, the density of the cork can be calculated by dividing 5.7g by 23.5 cm³, resulting in a density of approximately 0.243g/cm³. Therefore, choice A, 0.243g/cm³, is the correct answer as it accurately represents the density of the cork based on the provided values.
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What is the term for the reactant that is fully consumed by the reaction?
- A. limiting reactant
- B. reducing agent
- C. reaction intermediate
- D. reagent
Correct Answer: A
Rationale: The correct answer is 'limiting reactant.' In a chemical reaction, the limiting reactant is the substance that is entirely consumed when the reaction proceeds. It determines the extent of the reaction and limits the amount of product that can be formed. The other choices, such as 'reducing agent,' 'reaction intermediate,' and 'reagent,' do not specifically refer to the reactant that is fully consumed in the reaction.
Which of the following substances is the most dense?
- A. A block of gold weighing 12g and occupying 4.6cm³
- B. A cube weighing 6g and having a volume of 0.91cm³
- C. A block weighing 143g and with a volume of 24.3cm³
- D. None of the above
Correct Answer: B
Rationale: Density is calculated by dividing the mass of an object by its volume. For Choice A, the density is 12 g / 4.6 cm³ = 2.61 g/cm³. For Choice B, the density is 6 g / 0.91 cm³ = 6.59 g/cm³, making it the most dense option. For Choice C, the density is 143 g / 24.3 cm³ = 5.88 g/cm³. Therefore, Choice B, the cube weighing 6 g and having a volume of 0.91 cm³, is the most dense substance among the options provided.
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.
What can be predicted by using the periodic table?
- A. The properties of each of the elements
- B. The charges of polyatomic ions
- C. The number of isotopes in each element
- D. The potential for the discovery of new elements
Correct Answer: A
Rationale: The periodic table is a fundamental tool in chemistry that organizes elements based on their properties. By using the periodic table, scientists can predict the properties of each element. The arrangement of elements in the table groups together elements with similar characteristics, allowing for the prediction of various properties such as reactivity, atomic size, and electronegativity. These predictions are possible because elements in the same group or period exhibit similar chemical behaviors. Therefore, the correct answer is A: The properties of each of the elements.
Which of the following must be present in order to be considered an organic molecule?
- A. H
- B. O
- C. N
- D. C
Correct Answer: D
Rationale: To be considered an organic molecule, carbon (C) must be present. Organic molecules are primarily composed of carbon atoms bonded to hydrogen (H) atoms, along with other elements like oxygen (O), nitrogen (N), sulfur, and phosphorus. Carbon is the backbone of organic compounds due to its unique bonding properties and ability to form long and complex chains, making it an essential element in organic chemistry. While hydrogen, oxygen, and nitrogen are commonly found in organic molecules, it is the presence of carbon that defines a compound as organic. Without carbon, a molecule cannot be classified as organic, regardless of the presence of other elements.