Calculating Density of NH3: Step-by-Step Guide

  • Thread starter Thread starter Bradracer18
  • Start date Start date
  • Tags Tags
    Density
Click For Summary

Discussion Overview

The discussion revolves around calculating the density of ammonia (NH3) using its molecular weight and properties of gases at standard temperature and pressure (STP). Participants explore the relationship between molecular weight, volume, and density, while addressing potential confusion regarding unit conversions and the ideal gas law.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant states the molecular weight of NH3 is 17.03 g/mol and mentions the actual density as 0.771 kg/m^3.
  • Another participant suggests using the ideal gas law to relate the number of moles of gas at STP to its volume.
  • A participant expresses confusion about how to relate the volume of an ideal gas at STP to density, questioning the unit consistency when dividing mass by volume.
  • A later reply corrects the volume of an ideal gas at STP to 22.4 L/mol and advises converting this to cubic meters for consistency in units.
  • One participant reports calculating a density of 0.760 kg/m^3 after resolving their confusion.
  • Another participant notes that the volume of 22.4 L/mol may vary slightly for different gases, suggesting that accepted values can differ.

Areas of Agreement / Disagreement

Participants generally agree on the use of the ideal gas law and the molecular weight of NH3, but there is some uncertainty regarding the exact density value and the implications of variations in gas properties.

Contextual Notes

Participants express uncertainty about unit conversions and the application of the ideal gas law, indicating potential limitations in their understanding of how to derive density from molecular weight and volume at STP.

Bradracer18
Messages
203
Reaction score
0

Homework Statement



OK, the problem says to find the molecular weight of NH3.

It is 17.03g/mol.

Next, you are supposed to find the density(in Kg/m^3) for the NH3.

I'm not sure how you do this part. I don't know if I have to convert or what.

I know the actual density is 0.771 kg/m^3.

Homework Equations



D=M/V

The Attempt at a Solution

 
Physics news on Phys.org
It's a gas, you can probably treat it with the properties of an ideal gas. Like so many mols of an ideal gas at STP has a certain volume...etc. Think ideal gas law.

Does that help?
 
Well kinda I guess.

I know my chemistry(a little)...but I'm just confused(or thinking too much).

I know that at STP...volume is 22.4 L

Temp is 273.15K
Pressure is 1 atm
n is usually 1 mole

So how does that relate to density though...do i just divide my mass by the 22.4?(I can't see the units working out)
 
Small correction: at STP, the volume of an ideal gas is 22.4 L/mol. Liters are a way of expressing volume, right? So convert that to m^3. You already figured out the molecular mass per mol. Just look at the units (make sure everything is consistent).
 
ok...got that figured out...thanks for your help. Came out to be .760kg/m^3.
 
Yeah, the 22.4 L/mol isn't exactly the same for all gases, so depending on where you got the accepted value it might vary a bit.
 

Similar threads

Replies
7
Views
3K
  • · Replies 4 ·
Replies
4
Views
9K
  • · Replies 20 ·
Replies
20
Views
7K
  • · Replies 1 ·
Replies
1
Views
5K
Replies
3
Views
3K
Replies
4
Views
5K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 16 ·
Replies
16
Views
1K
  • · Replies 1 ·
Replies
1
Views
8K