A gas occupies 2.0 L at 1.0 atm. If pressure is increased to 4.0 atm at constant temperature, the volume will be:
A. 1.0 L
B. 8.0 L
C. 0.5 L
D. 2.0 L
Answer: Option C
Solution (By JKExamLibrary)
Boyle's law: P₁V₁ = P₂V₂. Given P₁=1.0 atm, V₁=2.0 L, P₂=4.0 atm. V₂ = (1.0 × 2.0) / 4.0 = 0.5 L. Volume decreases as pressure increases, because gas is compressible. The product PV is constant for a fixed mass of gas at constant T. Scuba divers experience this; as they dive deeper, pressure increases, reducing air volume in lungs.
Explanation:
Rusting is a chemical change because iron reacts with atmospheric oxygen and moisture to form hydrated iron(III) oxide. This new compound possesses entirely different chemical properties from the original iron. The process involves the formation of new chemical bonds and cannot be easily reversed by simple physical methods.
Explanation:
Boron trifluoride (BF₃) has covalent bonds where boron shares three electrons with three fluorine atoms. Although BF₃ can accept a lone pair to form coordinate bonds (as in BF₄⁻), its own bonds are polar covalent. Ionic bonding occurs between metal and non-metal.
Explanation:
Manganese is extracted by the aluminothermic process (Goldschmidt thermite process) where Mn₃O₄ is reduced by aluminium: 3Mn₃O₄ + 8Al → 9Mn + 4Al₂O₃. This works for metals with less reactivity than Al but not too reactive. Sodium is extracted by electrolysis. Iron is extracted by smelting with coke. Zinc by carbon reduction/electrolysis.
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