A gas of unknown molecular mass was allowed to effuse through a small opening under constant-pressure conditions. It required 10
5 s for 1.0 L of the gas to effuse. Under identical experimental conditions it required 31 s for 1.0 L of O2 gas to effuse. Calculate the molar mass of the unknown gas. (Remember that the faster the rate of effusion, the shorter the time required for effusion of 1.0 L; in other words, rate is the amount that diffuses over the time it takes to diffuse.)
1 answer:
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Answer: A. -396 kJ
Explanation:
The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.
Reversing the reaction, changes the sign of
On multiplying the reaction by 2, enthalpy gets multiplied by 2:
Thus the enthalpy change for the reaction is -396 kJ.
