Nokea
What is the general reaction for neutralizing acids and bases?
- A. Acid + base → water + salt
- B. Base + water → acid + salt
- C. Salt + water → acid + base
- D. Acid + base → water + salt
Correct Answer: D
Rationale: The correct general reaction for neutralizing acids and bases is when an acid reacts with a base, it forms water and a salt. This reaction is commonly known as a neutralization reaction. The hydrogen ions from the acid combine with the hydroxide ions from the base to form water, while the anion from the acid combines with the cation from the base to form a salt.
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Which of the following substances is most dense?
- A. A block of gold weighing 12g and having a volume of 4.6cm³
- B. A cube weighing 6g and having a volume of 0.91cm³
- C. A block weighing 143g and having a volume of 24.3cm³
- D. None of the above.
Correct Answer: B
Rationale: The correct answer is 'B: A cube weighing 6g and having a volume of 0.91cm³.' Density is calculated as mass divided by volume. For each option: A) 12g/4.6cm³ ≈ 2.61 g/cm³, B) 6g/0.91cm³ ≈ 6.59 g/cm³, C) 143g/24.3cm³ ≈ 5.88 g/cm³. Therefore, option B is the most dense with a density of approximately 6.59 g/cm³.
What occurs to an atom with a negative charge?
- A. Gained an electron
- B. Lost an electron
- C. Gained a proton
- D. Lost a proton
Correct Answer: A
Rationale: When an atom has a negative charge, it means it has gained an electron. Electrons are negatively charged particles, so when an atom gains an electron, it becomes negatively charged. This process is known as gaining an electron to achieve stability through a full outer electron shell. Atoms gain or lose electrons to attain a stable electron configuration, typically following the octet rule. In this case, gaining an electron is the correct choice as it results in the atom having a negative charge.
What is the mass of ethyl alcohol that will exactly fill a 200.0 mL container?
- A. 157.8 g
- B. 25.49 g
- C. 0.39 g
- D. None of the above
Correct Answer: A
Rationale: To determine the mass of ethyl alcohol required to fill a 200.0 mL container, we apply the formula Mass = Volume x Density. Given that the volume is 200.0 mL and the density of ethyl alcohol is 0.789 g/mL, the calculation becomes Mass = 200.0 mL x 0.789 g/mL = 157.8 g. Therefore, the correct answer is A, 157.8 g, as this is the mass of ethyl alcohol needed to completely occupy the 200.0 mL container.
What is the atomic number of a mystery element that has 6 protons, 6 electrons, and 6 neutrons?
- A. 6
- B. 12
- C. 18
- D. Not enough information
Correct Answer: A
Rationale: The atomic number of an element is equal to the number of protons in its nucleus. Since the mystery element has 6 protons, its atomic number is also 6. The number of neutrons and electrons does not affect the atomic number. Protons determine the element's identity, while neutrons and electrons affect its mass and charge, respectively. Therefore, choice A, 6, is the correct answer.
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.