Nokea
What is the name of the device that separates gaseous ions by their mass-to-charge ratio?
- A. mass spectrometer
- B. interferometer
- C. magnetometer
- D. capacitance meter
Correct Answer: A
Rationale: The correct answer is a mass spectrometer. A mass spectrometer is a device specifically designed to separate gaseous ions based on their mass-to-charge ratio. The separation occurs as ions pass through the mass spectrometer, allowing for the identification and quantification of compounds present in a sample. This analytical instrument is widely used in chemistry and other scientific fields due to its ability to provide detailed information about the composition of substances.
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What volume of silver will weigh exactly 2500.0 g? The density of silver is 10.5 g/cm³.
- A. 262.50 cm³
- B. 238.1 cm³
- C. 0.0042 cm³
- D. None of the above
Correct Answer: B
Rationale: To find the volume of silver, we use the formula: Volume = Mass / Density. Plugging in the given values, Volume = 2500.0 g / 10.5 g/cm³ = 238.1 cm³. Therefore, the correct answer is 238.1 cm³, which corresponds to option B.
When propane is reacted in the presence of oxygen gas, the products of this combustion reaction are:
- A. C + H2
- B. CH2 + H2O
- C. CO2 + H2
- D. CO2 + H2O
Correct Answer: D
Rationale: When propane undergoes combustion in the presence of oxygen, it forms carbon dioxide (CO2) and water (H2O). The balanced chemical equation for this reaction is: C3H8 + 5O2 -> 3CO2 + 4H2O. This means that three molecules of carbon dioxide and four molecules of water are produced when one molecule of propane reacts with five molecules of oxygen. Therefore, option D (CO2 + H2O) is the correct answer.
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).
Where are protons held within an atom?
- A. Nucleus
- B. Orbitals
- C. Electron cloud
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Nucleus. Protons are held in the nucleus, the central part of an atom where both protons and neutrons are located. Protons carry a positive charge and are specifically found within the nucleus. Orbitals and the electron cloud are regions where electrons are located surrounding the nucleus, not protons. Understanding the basic structure of an atom is fundamental in chemistry, where the nucleus serves as the core that contains the majority of the atom's mass and positive charge due to the presence of protons. This knowledge is crucial for grasping various chemical concepts and explaining the behavior of elements in chemical reactions.
Identify the reactants in the chemical reaction below: CH₄ + 2O₂ → CO₂ + 2H₂O
- A. CHâ‚„ and Oâ‚‚
- B. COâ‚‚ and Hâ‚‚O
- C. Both
- D. None of the above
Correct Answer: A
Rationale: Reactants in a chemical reaction are the initial substances that are transformed into products. In this reaction, CHâ‚„ (methane) and Oâ‚‚ (oxygen) are the reactants, as they are the starting materials that undergo a chemical change to form COâ‚‚ (carbon dioxide) and 2Hâ‚‚O (water). The equation clearly shows that CHâ‚„ and Oâ‚‚ are on the left side of the reaction arrow, indicating that they are the reactants. Therefore, the correct answer is A: CHâ‚„ and Oâ‚‚.