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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: JackB34 on July 18, 2022, 07:25:06 AM

Title: What exactly is the change in boiling point between soft and hard water?
Post by: JackB34 on July 18, 2022, 07:25:06 AM

As the title says I would like to know what exactly the boiling point change is between soft water (<80ppm) and hard water (it doesn’t really matter what ppm just as long as the ppm is given).

I am currently conducting an experiment to test the difference in properties between soft, hard and very hard water. Unfortunately as this is part of a year 11 test we were unable to procure very hard water so I have to use theoretical results. I have attempted to find a more exact statistic regarding the correlation between a water samples higher ppm and it's higher boiling point but have been unable to find anything more than a general agreement that there is a correlation. If anyone has an exact or semi-exact number regarding how much the temperature increases for a water sample with 200ppm that would be fantastic. If someone has a similar figure for a different ppm that would be equally helpful.

Title: Re: What exactly is the change in boiling point between soft and hard water?
Post by: DrCMS on July 18, 2022, 11:18:39 AM

Have you tried to calculate this? 
Even for very very hard water the increase in boiling point is going to be much less than 0.1°C.   

Title: Re: What exactly is the change in boiling point between soft and hard water?
Post by: JackB34 on July 18, 2022, 08:22:54 PM

I'm happy to calculate it and did attempt to do so I'm just not exactly sure where to start as I don't really have any point of reference. It did occur to me while writing this that I may be able to use the boiling point of sea water and find the increase in boiling point from there by calculating how many ppm cause a degree of difference.

Title: Re: What exactly is the change in boiling point between soft and hard water?
Post by: Borek on July 19, 2022, 03:22:50 AM

Quote from: JackB34 on July 18, 2022, 08:22:54 PM

I'm happy to calculate it and did attempt to do so I'm just not exactly sure where to start as I don't really have any point of reference.

Note that you won't get a single, simple answer, as there is no simple relationship between water hardness and solution composition. Solutions containing 2.6 g of dissolved CaSO₄ per 1 L and 1.8 g of MgCl₂ per liter have the same hardness, but different boiling points because of different van 't Hoff factors.