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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: catisioo on January 22, 2020, 02:53:26 AM

Title: Question about dissolving Ammonia
Post by: catisioo on January 22, 2020, 02:53:26 AM

This is a question from my countrys chemistry olympiad which I can't figure out. I have the correct answer but there are no explanations on how to get them. The question goes like this:

"A flask, which is filled up with ammonia, is filled with water so that all the ammonia dissolves. What is the mass concentration (%) of the solution? What is the molar concentration of the solution?"

The correct answer is 0.076 for the mass concentration and 0.045 for the molar concentration. If there was a solubility curve or some data to work with, this would be easy but there is none. I am confused. How is it possible to know this?

Title: Re: Question about dissolving Ammonia
Post by: Borek on January 22, 2020, 03:03:24 AM

Quote from: catisioo on January 22, 2020, 02:53:26 AM

all the ammonia dissolves

Do you need solubility if you are told everything dissolved?

Title: Re: Question about dissolving Ammonia
Post by: AWK on January 22, 2020, 04:16:49 AM

Assume that you have a 1L bottle filled with ammonia under STP. Then pour 1 L of water into it. The solubility of ammonia in water is very high (700 L of NH₃ / 1L water). Calculating the percentage and molar concentration is already very easy (the solution will be so diluted that you do not have to worry about the density of the solution).