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An electric kettle has two heating coils. When one of the coils is connected to an A.C source, the water in the kettle boils in 10 minutes. When the other coil is used the water boils in 40 minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be: (A) 8 min (B) 4 min (C) 25 min (D) 15 min

Let us suppose, resistance of the two coils be R1 and R2 Voltage supplied = V Effective resistance of two coils in parallel = (R1.R2) /(R1+R2)... View Article

Assuming that water vapour is an ideal gas, the internal energy change (ΔE) when 1mol of water is vapourised at 1 bar pressure and 100°C, (given : molar enthalpy of vapourisation of water at 1 bar and 373K = 41kJ mol–1and R = 8.3J mol–1K–1 ) will be: (a) 4.100 kJ mol-1 (b) 3.7904 kJ mol-1 (c) 37.904 kJ mol-1 (d) 41.00 kJ mol-1

Answer: (c) 37.904 kJ mol-1 H2O(l) ⇌ H2O(g) Given, the internal energy change (ΔE) Molar enthalpy of vapourisation of water at... View Article