4. Find the standard enthalpy of formation of ethylene, C2H4(g), given the following data: heat of combustion of C2H4(g) = â€"1411 kJ/mol; ď„H°f[CO2(g)] = â€"393. 5 kJ/mol; ď„H°f[H2O(l)] = â€"285. 8 kJ/mol.

Ans. : frostbite is when exposure to cold temperatures causes freezing to the skin or other tissues. it most commonly affects the hands, feet, and face. the longer areas are exposed to cold, typically the worse the frostbite. the water temperature used for rewarming a frostbitten part should be : (102 -105) f degrees.

The net force is 100

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