Solder is an alloy primarily used for welding electrical components and pipes. It is traditionally composed of lead (Pb) and tin (Sn), typically in a 60:40 or 50:50 ratio. Brass is copper and zinc, bronze is copper and tin, and duralumin is an alloy of aluminum, copper, magnesium, and manganese.
Explanation:
Potassium (K) is at the top of the reactivity series, meaning it is the most reactive among the given metals. The order of reactivity (decreasing): K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Ag > Au. Potassium reacts violently with water and oxygen. Copper (Cu) is relatively unreactive and is found native in nature. Exam trick: Remember 'Please Stop Calling Me A Cute Zebra...' mnemonic.
Explanation:
Soap (sodium/potassium salts of long-chain fatty acids) reacts with Ca²⁺ and Mg²⁺ ions in hard water to form insoluble calcium/magnesium salts (scum), which precipitates and does not lather. This wastes soap. Reaction: 2RCOONa + Ca²⁺ → (RCOO)₂Ca↓ + 2Na⁺. Detergents do not form scum because their calcium salts are soluble. Hardness is measured in ppm of CaCO₃.
Explanation:
Silver bromide decomposes into silver and bromine on exposure to light. This is a photochemical decomposition reaction, where a single compound breaks down into two or more simpler substances. It is also a redox reaction (Ag⁺ reduced, Br⁻ oxidized). Photographic films use this property. Combination would be A + B → AB. Displacement is A + BC → AC + B. Neutralization is acid + base → salt + water.
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