2.14 · Intro to Nuclear and Organic ChemistryPractice · 核化学与有机化学初步
This chapter is optional; AP Chemistry doesn’t test it.
Lessons covered:2.14.1 Types of Radioactive Decay2.14.2 Half-Life2.14.3 Fission and Fusion2.14.4 Hydrocarbons and Functional Groups
- 1Multiple choice
Household smoke detectors contain a tiny amount of (americium-241), which undergoes alpha decay. What nucleus forms?
ExplanationAn alpha particle is . Losing one lowers the mass number by 4 and the atomic number by 2: 241 − 4 = 237 and 95 − 2 = 93. Element 93 is neptunium, so forms. Dropping only the mass number would leave the element unchanged, which can’t be right; would take two alpha decays.
- 2Multiple choice
, released in nuclear accidents, decays to : → + X. What is X?
ExplanationNuclear equations conserve both mass number and charge. X has mass number 137 − 137 = 0 and charge 55 − 56 = −1: an electron, that is, a beta particle. In beta decay a neutron in the nucleus turns into a proton and emits an electron, so the element moves up one place to barium.
- 3Numeric
has a half-life of 138.376 days. What percentage of a polonium-210 sample remains after 365 days?
%ExplanationNumber of half-lives = 365 ÷ 138.376 = 2.638, not a whole number, so use the formula: fraction left = = = 0.161, or 16.1%. That sits between 2 half-lives (25%) and 3 (12.5%), as it should.
Review: 2.14.2 Half-Life
- 4Numeric
One way uranium-235 splits after absorbing a neutron: + x . What is x?
ExplanationMass number is conserved: 235 + 1 = 141 + 92 + x, so x = 3. Charge checks too: 92 + 0 = 56 + 36 + 0. The 3 neutrons released by each fission can split more uranium nuclei, setting up a chain reaction.
Review: 2.14.3 Fission and Fusion
- 5Multiple choice
The chain hydrocarbon with 4 carbon atoms and one carbon–carbon triple bond is 1-butyne. What is its molecular formula?
ExplanationAlkanes are CₙH₂ₙ₊₂, so butane is C₄H₁₀. Each double bond removes 2 H (1-butene is C₄H₈), and a triple bond counts as two, removing 4 H: C₄H₆, which fits the alkyne formula CₙH₂ₙ₋₂.
- 6Select all
Glycine, H₂N−CH₂−COOH, is the simplest amino acid. Which functional groups does it contain? (Select all that apply.)
More than one option may be correct. Choose all that apply, then press Submit.
Explanation−NH₂ is an amino group (basic) and −COOH is a carboxyl group (acidic). Amino acids have both, so they react with acids and with bases. The −OH inside −COOH is part of the carboxyl group, not a separate hydroxyl group, and there is no ester or C=C.
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