Common Chemical Compounds and Reactions

Microcosmic salt is sodium ammonium hydrogen phosphate tetrahydrate, with the formula Na(NH₄)HPO₄·4H₂O. It crystallizes in characteristic tetrahedral shapes and is used in qualitative analysis for detecting cations through flame tests. The exact number of water molecules (4) is crucial for identification. This salt forms when equimolar solutions of sodium phosphate and ammonium phosphate are mixed.

Among alkaline earth carbonates, solubility increases down the group. BeCO3 has the highest solubility due to the very small size and high charge density of Be²+ ion, which gives it exceptional hydration energy that overcomes lattice energy. MgCO3, CaCO3, and SrCO3 are progressively less soluble. SrSO4 is a sulfate (not carbonate) and is actually insoluble.

Carnallite is a naturally occurring mineral with the chemical formula KCl·MgCl₂·6H₂O. It is an important source of potassium and magnesium. Option A is borax, B is dolomite, and D is cryolite.

Epsom salt is the common name for magnesium sulfate heptahydrate, MgSO₄·7H₂O. It has been used traditionally as a bath salt for muscle relaxation. Option A is incorrect hydration state, B is gypsum, and C is washing soda.

BeO, Al₂O₃, and ZnO are amphoteric oxides - they react with both acids and bases. CaO is a basic oxide that only reacts with acids to form salts and water. It does not react with bases.

Baking soda is the common name for sodium bicarbonate (NaHCO₃). It is used in baking as a leavening agent because it decomposes on heating to release CO₂. Sodium carbonate (Na₂CO₃) is washing soda, and sodium sulfate (Na₂SO₄) is Glauber's salt.

Li2CO3 decomposes on heating because Li+ is very small and polarizes the large CO3^2- ion, weakening the C-O bonds and causing decomposition into Li2O and CO2. Na2CO3 and K2CO3 are stable to heat due to larger cations with lower polarizing power, while CaO is already an oxide and cannot decompose further.

Soda ash is the common name for anhydrous sodium carbonate, Na2CO3. Option A is baking soda (sodium bicarbonate), option B is washing crystals (hydrated sodium carbonate), and option C is caustic soda (sodium hydroxide).

CaCl2 is an excellent desiccant due to its high hygroscopicity - it readily absorbs water vapor from the air to form hydrated species. Na2CO3 can absorb some water but is less effective, NaCl is not hygroscopic enough, and Na2SO4 is used as a drying agent only after initial drying, not as a primary desiccator.

Potash alum is KAl(SO4)2·12H2O, a double sulfate containing potassium and aluminum in 1:1 ratio with 12 water molecules. Option B shows 2:1 stoichiometry with 24 waters, option C shows 2:1 with 6 waters - neither matches the correct formula of common potash alum.

Chalk powder is insoluble in water. Out of salt, sugar and baking powder, salt particles are the smallest in size and thus, get dissolved the fastest in water. 

Pearls are composed primarily of calcium carbonate (CaCO3) in the form of aragonite crystals, layered with conchiolin (an organic protein) to create the characteristic nacre structure. This combination gives pearls their luster and iridescence.

Gypsum is a very soft sulphate mineral composed of calcium sulphate dihydrate, with the chemical formula CaSO_4•2H₂O. Lithopone is a white pigment consisting of a mixture of barium sulphate (BaSO₄) and zinc sulphide (ZnS). Lithopone is a white pigment consisting of a mixture of barium sulphate (BaSO₄) and zinc sulphide (ZnS). Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H₂Mg₃(SiO₃)₄ or Mg₃Si₄O₁₀(OH)₂.

Bleaching powder is manufactured by the action of chlorine gas on dry slaked lime, which is calcium hydroxide. The chemical reaction yields calcium oxychloride, the active component of bleaching powder.

Soaps are sodium or potassium salts of long-chain monocarboxylic acids, commonly known as fatty acids. These carboxylic acids contain a single carboxyl group attached to a long hydrocarbon chain.