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Gas Law Problem

Nitrogen and Hydrogen gases react to form Ammonia. A closed, rigid cylinder contains a total of 0.750 mol of gas at 25 degrees C and 1.10 atm before the reaction takes place; the mole ratio of hydrogen to nitrogen in the cylinder is 3:2. Determine the temperature and pressure of the gas in the cylinder at the end of the reaction.

Assume the cylinder walls do not absorb nor release heat. Neither the temperature nor the pressure remains constant. Otherwise, make any assumptions necessary to solve the problem.

Solution Preview

N2(g) + H2(g) --> NH3(g)
This will be your overall reaction, but it needs to be balanced. The balanced reaction will look something like this:

N2(g) + 3H2(g) --> 2NH3(g)

Which means that we need 3x the amount of moles of hydrogen gas than nitrogen gas (see mole ratio in which they react). Out of the o.75 mole of gas in total there is a 3:2 ratio of hydrogen to nitrogen gas. Therefore we have 0.45 moles of hydrogen gas, and 0.30 moles of nitrogen gas.

N2 + 3H2 --> ...

Solution Summary

The solution clearly explains how to determine the temperature and pressure of gas in a closed cylinder after a reaction has taken place inside.