Ammonium hydroxide solution

[Zoe D]

Hi guys,

I am trying to make a 1 M solution of ammonium hydroxide (NH4OH) from a 25% stock solution. My problem is that every reference I come across (The Laboratory, various chemistry sites online) says that the molecular weight of the compound should be 35.1, yet the bottle I have states that the M.W. is 77.08. Why is there a difference and should I trust the bottle or not? The bottle is from Silform and is labelled Ammonia solution 25% tech. It then has the formula NH4OH.

Zoe

[Whspa]

Ammonium acetate has the molecular weight of 77.08.
I wouldn't trust the bottle. I've bought chemicals from Silform before and they've been wrongly labelled.
Try contacting Silform for their advice.

[Labbie]

Ammonium Hydroxide is Ammonia page 35 from csis The Lab book page 11 tells us Ammonia is 17.0 Is that any help.

[Zoe D]

Hmm, the plot thickens. I think I will try contacting Silform...

Thanks.

[fibreweb]

In my recipe book I have dilution figures for Ammonia at different percentages to make 1M.
From memory I sourced this information from reliable sources many years ago when I made up my table.
10% 178ml reagent/822 water for a litre volume
18% 105 ml/895 water
25% 75ml/925 water
28% 68ml/932 water
35% 55ml/945 water.
I also have a note that I wrote stating that different sources of reference may have slightly different figures, however for the purposes of school chemistry these very slight differences do not matter.

[labbassistant]

Hi all,
I'm a little confused with ammonia...
We have some droppers labelled Ammonia solution 0.1m, and then we have ammonium hydroxide solution 0.1m.
I was having a google and I'm not 100% sure but is ammonia the same as ammonium hydroxide? Or is ammonia the gas and ammonium hydroxide the solution?
Should I be relabeling?
Help! Thanks in advance

[ottenc]

Hi all,
I'm a little confused with ammonia...
We have some droppers labelled Ammonia solution 0.1m, and then we have ammonium hydroxide solution 0.1m.
I was having a google and I'm not 100% sure but is ammonia the same as ammonium hydroxide? Or is ammonia the gas and ammonium hydroxide the solution?
Should I be relabeling?
Help! Thanks in advance

Any diluted solution of ammonia is ammonium hydroxide. A bottle can be labelled with either, and programs like RiskAssess just list it as ammonia. As long as you are aware they are the same thing and can provide it no matter how the teachers ask for it, feel free to label it however you please

[labbassistant]

Hi all,
I'm a little confused with ammonia...
We have some droppers labelled Ammonia solution 0.1m, and then we have ammonium hydroxide solution 0.1m.
I was having a google and I'm not 100% sure but is ammonia the same as ammonium hydroxide? Or is ammonia the gas and ammonium hydroxide the solution?
Should I be relabeling?
Help! Thanks in advance

Any diluted solution of ammonia is ammonium hydroxide. A bottle can be labelled with either, and programs like RiskAssess just list it as ammonia. As long as you are aware they are the same thing and can provide it no matter how the teachers ask for it, feel free to label it however you please

Amazing! Thank you so much!!

[bigmack]

I had to make some 0.1M Ammonia solution .Our stock bottle is labeled 25% Ammonia .
I gotta say I am also totally confused .
I first tried Merck Acid/base calculator which includes Ammonium Hydroxide .
It was well until I scrolled down to where they base their calculations .They mention 28% Ammonia they sell is actually 56.5%ammoniam Hydroxide so that got me thinking that the too aren't the same thing . Am I making 0.1M ammonia solution or Ammonium Hydroxide solution ?
What is the 25% stock solution , Ammonia or Ammonium Hydroxide?
Is it 25% W/W or W/V ?

I did some googling and even looked here and now I am completely confused .
Seems everyone has a different opinion on it . There are forums of University boffins that are arguing .some say 25% is 14.7M , another says its 13.something .
It's all way above my pay grade .
I just want to make a solution .

In my recipe book I have dilution figures for Ammonia at different percentages to make 1M.
From memory I sourced this information from reliable sources many years ago when I made up my table.
10% 178ml reagent/822 water for a liter volume
18% 105 ml/895 water
25% 75ml/925 water
28% 68ml/932 water
35% 55ml/945 water.
I also have a note that I wrote stating that different sources of reference may have slightly different figures, however for the purposes of school chemistry these very slight differences do not matter.

That would mean 7.5ml made up to 1Litre for 0.1M


One online answer is this . It is saying use 15.41mls of 25% made up to 1Litre for 0.1M
https://askfilo.com/user-question-answe ... 3538353236

Google AI calculates it as 6.8ml made up to 1 liter
based on 25% ammonia having a molarity of 14.7Mol/L
From here
https://www.vedantu.com/question-answer ... 56229a534f.

I'm buggered if I know how to do it

[Marama T]

Ammonium hydroxide is ammonia in water. Give yourself a break bigmack and just use the Merck calculator.

[bigmack]

Ammonium hydroxide is ammonia in water. Give yourself a break bigmack and just use the Merck calculator.

I realize that Ammonia in water is Ammonium Hydroxide and often called Ammonia.
This is the problem Marama, the default values in the Merck calculator say this when I use it .
(All I added was 1000mls and 0.1Molarity ).

Ammonia calculator.png

This is what it says about the 28% verses 56.6%

Ammonia description.png

So if I change the 56.6% to 25% , I get this .
It is now telling me that the Molarity of the 25% is only 6.419 M when everywhere else suggests that it is 14.7 M

Ammonia 25%.png

[bigmack]

Thinking about this some more .
Looking at Merck calculator that they base on their 28% product . They say 6.88ml per litre .

When I look back at Fibrewebs post , it also says 6.8ml per litre iff’n it was 0.1m from 28%

So I am confident that Fibrewebs 7.5mls for 25% would be pretty close to the mark .

Incidentally , I did make up the solution using the 28% figure from Merck yesterday and the prac was done . Haven’t heard back

[Marama T]

I found this very confusing too. I relabelled all our "ammonia" with "ammonium hydroxide" just to make things clearer.

[RosalieL]

I think it's like when you have copper sulfate anhydrous which is 159.6g/mol but copper sulfate pentahydrate is 249.68g/mol. If you make up a 5% solution of copper sulfate anhydrous by weight (5g CuSO4/95gH2O) you will have a different molarity compared to a 5% solution of pentahydrate (5gCuSO4.5H2O/95gH2O).

So with the "ammonia", only the concentration of ammonia NH3 is being considered but "ammonium hydroxide" is counting all the oxygen molecules making the NH4+ and OH- ions, so it's a higher percentage of the solution. Your first calculation screenshot would be correct.

[Marama T]

Did you find out how the prac went bigmack?

[Marama T]

I went searching online and hit the same problem - different molarities for 25% based on whether they were using the molecular weight of ammonia or ammonium hydroxide in their calculations. Check out the different molarities on this page
https://www.google.com/search?udm=14&q= ... ve&ssui=on
It's a fabulous conundrum worthy of further investigation. Thanks for making my brain hurt (again) bigmack.