Calculate the mass of nitrogen dissolved

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Discussion Overview

The discussion revolves around calculating the mass of nitrogen dissolved in a home aquarium under specific conditions, including total pressure and mole fraction. The context includes a homework problem that requires applying gas laws and potentially Henry's Law.

Discussion Character

  • Homework-related, Mathematical reasoning, Technical explanation

Main Points Raised

  • Joe presents an attempt to calculate the mass of nitrogen dissolved using the ideal gas law, providing specific values for pressure, volume, and temperature.
  • One participant points out that the calculation cannot be completed without the Henry's Law constant for nitrogen.
  • Another participant clarifies that Joe's calculated mass represents the mass of nitrogen gas at a given pressure, not the mass that is actually dissolved in the aquarium.
  • Joe acknowledges that using Henry's Law allowed him to find the correct relationship for the homework assignment and mentions that constants will be provided for the exam.

Areas of Agreement / Disagreement

Participants generally agree that the initial calculation does not yield the mass of nitrogen dissolved, but rather the mass of nitrogen gas. There is no consensus on the specific values or constants needed for the correct calculation.

Contextual Notes

The discussion highlights the importance of Henry's Law in determining the mass of gas dissolved in a liquid, indicating that the absence of necessary constants can lead to incorrect conclusions.

Who May Find This Useful

Students working on gas law applications, particularly in chemistry or environmental science contexts, may find this discussion relevant.

Agent M27
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Homework Statement



Calculate the mass of nitrogen dissolved at room temperature in a 92.0 L home aquarium. Assume a total pressure of 1.0 atm and a mole fraction for nitrogen of 0.78.

Homework Equations



PV=nRT

The Attempt at a Solution



P_{total}=1 atm

P_{N}=.78 atm

V=92LSo here is what I did:
n=\frac{PV}{RT} = \frac{(.78)(92)}{(.08206)(298.15)}

n=2.93303

mass = (2.93303 mol)\frac{28.02g}{mol}

mass = 82.1834g

This is an online homework assignment and it keeps rejecting my answer. It only wants two sig figs. Any ideas where I am going wrong? Thanks in advance.

Joe
 
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You can't solve this unless Henry's Law constant or Proportionality Constant (in Henry's Law) for Nitrogen is given
 
The mass you calculated is not the mass DISSOLVED.
Instead it is the mass of Nitrogen gas that would be present in a container (evacuated) of 92L at a pressure of 0.78 atm
 
Thanks guys, the Henry's law relationship worked out. This was an online HW so we were allowed to look certain constants up. For the exam he will provide the necessary constants.

Joe
 

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