Carbon-14 (half-life ~5730 years) is used to determine the age of archaeological and geological organic samples up to ~50,000 years. Cobalt-60 for cancer; Am-241 for smoke detectors.
Explanation:
Hard water contains dissolved Ca²⁺ and Mg²⁺ ions which react with soap to form insoluble scum, preventing lather. Soft water lathers readily. Distilled water is pure (soft). Rainwater is naturally soft but may dissolve CO₂ and become slightly acidic.
Explanation:
Combination: two or more reactants combine to one product. Mg and O₂ combine to form MgO. A is decomposition; B is displacement; D is double displacement.
Explanation:
Normal rainwater is slightly acidic (pH ~5.6) due to the dissolution of atmospheric CO2 forming carbonic acid. Acid rain is defined as precipitation with a pH lower than 5.6. It is caused by emissions of sulfur dioxide and nitrogen oxides, which react with water to form stronger sulfuric and nitric acids.
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