When liquid nitrogen is boiled to make gaseous nitrogen, is it endothermic or exothermic process?
In this reaction, is the work done "on" the system or "by the system" or none?
2006-10-02 17:45:54 · 5 answers · asked by Karan S 1 in Science & Mathematics ➔ Chemistry
The boiling of liquid nitrogen to form gaseous nitrogen is no different than the boiling of water to form water vapor. Heat is absorbed by the system during this transformation, hence the reaction is endothermic. The amount of heat needed to transform 1 mole of liquid N2 to gaseous N2 at the boiling point is given by the molar enthalpy of vaporization.
Because the molar volume of nitrogen gas is larger than the molar volume of liquid nitrogen, this process results in a positive change in volume. The work done *by* an expansion process is equal to P* (V_final - V_initial) = P* delta_V. V_final and V_inital are the final and initial volumes of the system, respectively. Here, V_final >> V_initial, so the change in volume is large and positive. As long as the ambient pressure (P) is greater than zero, the system is allowed to expand, the system does work *on* the surroundings (work is done *by* the system).
If the expansion of a boiling liquid caused work to be done *on* the system, then steam engines wouldn't exist!
If P = 0, that is, if the gas expands into a vacuum, or against a piston that has a vacuum on the other side, then P*delta_V = 0 * delta_V = 0, and no work is done, either on the system or by the system.
2006-10-02 18:17:54 · answer #1 · answered by hfshaw 7 · 0⤊ 0⤋
In endothermic reactions heat (enery/work) is absorbed by the reacting material to give the products. Therefore since you are heating nitrogen it is an endothermic reaction. Work is done on the system to convert it from liquid to gas.
2006-10-03 00:52:36 · answer #2 · answered by ssrirag2001 2 · 0⤊ 1⤋
Endothermic...think "endo" means "in," therefore work has to be done on the system for the reaction to occur.
2006-10-03 00:48:59 · answer #3 · answered by Richard H 2 · 0⤊ 1⤋
As the nitrogen boils, it absorbs heat from its surroundings. Work is done "on" the nitrogen.
2006-10-03 00:50:18 · answer #4 · answered by ? 6 · 0⤊ 1⤋
endo. gases are at a higher energy state than liquids & solids. Therefore it must be endo.
From liquid to solid would be exo, because it would be loosing energy to the surrounding system.
2006-10-03 00:50:31 · answer #5 · answered by Anonymous · 0⤊ 1⤋