Ammonium Chloride Addition Calculation

[KingBlingTX]

Can someone double check my calculation on this? If I add 1.5 grams of Ammonium Chloride to 48 gallons of saltwater water, what should the ammonia concentration in ppm be once it is mixed?

This is what I calculated (neglecting any NH3 loss to atmosphere).
MW of NH4Cl = 53.49 g/mol
in solution the NH4+ + Cl- <=> NH3 + H+ + Cl- (essentially a 1:1 molar ratio of NH4 to NH3 since the reaction is strongly favored to the right)
MW of NH3 = 17.03 g/mol; that means it's 31.8% by mass of the NH4Cl molecule
So, 1.5 grams NH4Cl x 31.8% x 1/48 gal x 1 gal/3.785 liter = 2.6 mg/L or ppm

Is this correct? I added that amount to cycle a new tank and I'm getting NH3 concentration much greater than 5 ppm on my test.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, that is correct.

 

[KingBlingTX]

Thanks, Randy. I thought I must have missed something. Obviously, my scale must not have been correct.

 

[Randy Holmes-Farley Verified Community Expert]

Or maybe the kit is off.

 

[JimWelsh]

Can someone double check my calculation on this? If I add 1.5 grams of Ammonium Chloride to 48 gallons of saltwater water, what should the ammonia concentration in ppm be once it is mixed?

This is what I calculated (neglecting any NH3 loss to atmosphere).
MW of NH4Cl = 53.49 g/mol
in solution the NH4+ + Cl- <=> NH3 + H+ + Cl- (essentially a 1:1 molar ratio of NH4 to NH3 since the reaction is strongly favored to the right)
MW of NH3 = 17.03 g/mol; that means it's 31.8% by mass of the NH4Cl molecule
So, 1.5 grams NH4Cl x 31.8% x 1/48 gal x 1 gal/3.785 liter = 2.6 mg/L or ppm

Is this correct? I added that amount to cycle a new tank and I'm getting NH3 concentration much greater than 5 ppm on my test.

Very nice to see someone actually do the math, and then come here for verification, rather than simply asking to be spoon-fed an answer. You must be one of those admirable few who did not sleep through algebra class! Well done.

 

[Cory]

Everyone has their role in life. If it wasnt for me and others, you wouldnt have gas in your car. Unless you want to go and dig it out yourself? Joking

 

[JimWelsh]

Everyone has their role in life. If it wasnt for me and others, you wouldnt have gas in your car. Unless you want to go and dig it out yourself? Joking

I apologize if I offended you, or anyone else. Upon reflection, there is a good argument to be made that such "spoon feeding" is one of the very reasons this forum exists. I'll try to roll the 'tude back a notch or two.

 

[mcarroll]

I will say that I'm not that fluent in moles, though I did OK in physics and chemistry in school. I just don't have cause to do any calculations...well...almost ever. I dose commercial solutions or I follow RHF's Recipe...

So to me it's really refreshing to see the math worked out verbosely on these chemistry questions! I really appreciate it!!

And I agree also that some spoon feeding is called for - on many topics - and has to be considered some part of the reason for R2R.

 

[Malte]

Hi all! Seemingly the only place on the Interwebs where this calculation is being discussed! Thanks for posting it!

What I find curious is that my readings are far below those of KingBlingTX. I am doing a fishless cycle with NH4Cl in my 58 gal tank and should be getting just over 8 ppm of NO3. Instead, I am getting a reading of just 5 ppm NO3 in the system. At the same time, there is virtually no NH3/NH4 or NO2 left in my tank. Are the JBL water tests et al all just somewhat inaccurate?

 

[Malte]

Coming to think of it, I guess I am likely losing Nitrogen into the atmosphere. Anyways, thanks a lot for this thread!

 

[AdamLajner]

Can someone double check my calculation on this? If I add 1.5 grams of Ammonium Chloride to 48 gallons of saltwater water, what should the ammonia concentration in ppm be once it is mixed?

This is what I calculated (neglecting any NH3 loss to atmosphere).
MW of NH4Cl = 53.49 g/mol
in solution the NH4+ + Cl- <=> NH3 + H+ + Cl- (essentially a 1:1 molar ratio of NH4 to NH3 since the reaction is strongly favored to the right)
MW of NH3 = 17.03 g/mol; that means it's 31.8% by mass of the NH4Cl molecule
So, 1.5 grams NH4Cl x 31.8% x 1/48 gal x 1 gal/3.785 liter = 2.6 mg/L or ppm

Is this correct? I added that amount to cycle a new tank and I'm getting NH3 concentration much greater than 5 ppm on my test.

Hi, quite late for discusion. very newbie here. Im trying to calculate if i know ppm of NH4+Cl, how to calculate NH3 with fresh water. How do you come up with molar ratio 1:1?

 

[Randy Holmes-Farley Verified Community Expert]

Hi, quite late for discusion. very newbie here. Im trying to calculate if i know ppm of NH4+Cl, how to calculate NH3 with fresh water. How do you come up with molar ratio 1:1?

I think this is best addressed in your other thread, but I question the basis of the need. Why would you want it 1:1? To do that you need the pH to be at the pKa for ammonia. The exact value depends on the other ions present, but is about 9.3 in seawater.

 

[AdamLajner]

I think this is best addressed in your other thread, but I question the basis of the need. Why would you want it 1:1? To do that you need the pH to be at the pKa for ammonia. The exact value depends on the other ions present, but is about 9.3 in seawater.

That is what i was wondering how to get that molar ratio

 

[Randy Holmes-Farley Verified Community Expert]

That is what i was wondering how to get that molar ratio

In the graph below from the article linked above, it comes from pH and knowing the properties of ammonia:

Ammonia and the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com

Figure 1. The fraction of free ammonia (NH3) and ammonium ion (NH4+) present in seawater as a function of pH.