Questions and Answers
Which of the following lists the samples in order of increasing number of moles in the sample?
In addition to Avogadro's number, which of the following must the student know to determine the number of molecules in a pure solid sample?
Which numerical expression gives the number of particles in 2.0g of Ne?
(2.0g/20.18 g/mole)(6.0x10^23 particles/mol)
The mass spectrum of the element Sb is most likely represented by which of the following?
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Which element has the mass spectrum represented above?
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The peak at 26 amu in the mass spectrum represents an isotope of which element?
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What is the formula unit of each compound with different ionic compounds containing copper and chlorine?
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Which sample has the higher purity based on percent by mass of chlorine?
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Which has the greater molar mass, X or Z?
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What information could be used to determine which mixture has the higher proportion of KCl?
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Which columns provide all the information necessary to determine the mole ratio of Ca to Mg in the rock?
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What quantities are needed to determine if the sample is pure MgCl2?
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Which ground-state electron configuration represents the atom with the lowest first-ionization energy?
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What is the ground-state electron configuration of the F− ion?
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What represents the ground-state electron configuration for an atom of selenium?
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Which electron configuration is consistent with the complete photoelectron spectrum?
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What observation would provide evidence that the spectrum is consistent with the atomic model?
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How is the photoelectron spectrum consistent with the electron shell model of the atom?
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Study Notes
Moles and Sample Masses
- In comparing 1g samples of NaCl, KBr, and KCl, the order of increasing number of moles is KBr < KCl < NaCl.
- To determine the number of molecules in a pure solid compound, knowledge of molar mass and mass of the sample is essential.
- The calculation for the number of particles in 2.0g of Ne involves using the formula: (2.0g/20.18 g/mole) × (6.0 × 10^23 particles/mol).
Mass Spectrum Analysis
- The mass spectrum of antimony (Sb) shows peaks at atomic mass units (amu) 121 and 123.
- Molybdenum (Mo) is identified as having a mass spectrum aligning with these amu values.
- The presence of a peak at 26 amu in a mass spectrum indicates an isotope of magnesium (Mg) with 14 neutrons.
Ionic Compound Analysis
- An elemental analysis of two copper-chlorine ionic compounds can help determine their formula units based on differences observed.
- Measuring the percent by mass of chlorine in two NaCl samples helps identify which has higher purity if KCl is the only contaminant.
- Comparing the mass of residues after heating two unknown alkali metal chlorates allows determination of which compound has a greater molar mass between X and Z.
Mixtures and Composition
- Analysis of two 10g mixtures of NaCl and KCl can determine which has a higher proportion of KCl by assessing the mass of Cl in each.
- The mole ratio of calcium to magnesium in a mixed carbonate rock is derived from specific columns in a lab analysis table (3, 4, 6, 7).
- For assessing purity in a 5.0g sample of MgCl2, knowledge of both the mass of Mg and the mass of Cl is crucial.
Electron Configurations
- The lowest first-ionization energy corresponds to the ground-state electron configuration of 1s²-2s²-2p⁶-3s¹.
- The electron configuration of the F⁻ ion is represented as 1s²-2s²-2p⁶.
- Selenium's ground-state electron configuration is illustrated as 1s²-2s²-2p⁶-3s²-3p⁶-4s²-3d¹⁰-4p⁴.
Photoelectron Spectroscopy
- An element's complete photoelectron spectrum can be consistent with the electron configuration of 1s²-2s²-2p⁶-3s²-3p³.
- If an element tends to form ions with a +1 charge, this provides evidence that its spectrum aligns with known atomic models.
- In the case of nitrogen, its photoelectron spectrum demonstrates that electrons in the 2p sublevel have the lowest binding energy.
Studying That Suits You
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Description
Test your knowledge of key concepts in AP Chemistry with these quizzes covering Units 1-4 and Unit 6. Each question dives into core ideas, such as molar relationships and the properties of compounds. Perfect for reinforcing your understanding and exam preparation.
