Carbon-14 is a radioactive isotope of carbon with a half-life of about 5,730 years. It is continuously formed in the atmosphere and incorporated into living organisms. When the organism dies, C-14 decays. By measuring the remaining C-14, scientists can determine the age of archaeological and geological samples up to ~50,000 years old.
Explanation:
Phenolphthalein is a synthetic acid-base indicator, organic compound prepared in the lab. Litmus is a natural dye from lichens. Turmeric is a natural indicator (yellow in acid, reddish brown in base). Red cabbage juice is natural. Synthetic indicators are often used in titrations: methyl orange, phenolphthalein.
Explanation:
Oxidation is loss of electrons. Na loses an electron to become Na⁺, so it is oxidized. Options A, C, D involve gain of electrons (reduction). Oxidation also can be defined as gain of oxygen or loss of hydrogen. In the reaction, Na acts as reducing agent. Mnemonic: LEO (Loss of Electrons is Oxidation) GER (Gain of Electrons is Reduction).
Explanation:
V₂O₅ catalyzes the oxidation of SO₂ to SO₃ in the Contact process for sulfuric acid: 2SO₂ + O₂ ⇌ 2SO₃. Fe is used for ammonia (Haber). Pt-Rh gauze for nitric acid (Ostwald). Sodium hydroxide is made by chlor-alkali electrolysis, no catalyst needed. V₂O₅ is preferred over Pt because it is cheaper and less susceptible to poisoning by arsenic impurities.
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