Reef Chemistry Question of the Day #31 Hyposalinity

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #31

Well have an easier one for the Columbus Day holiday...

If an aquarist wanted to produce a hyposaline solution with a specific gravity of about 1.009, that can be best accomplished by mixing which of the following solutions?


A. Mixing 90% pure fresh water with 10% seawater (sg = 1.0264)
B. Mixing 66% pure fresh water with 34% seawater (sg = 1.0264)
C. Mixing 33% pure fresh water with 67% seawater (sg = 1.0264)
D. Mixing 13% pure fresh water with 87% seawater (sg = 1.0264)

Good luck!















.

 

[psirex]

B

Weighted Avg...

 

[reggaedrummin]

Math says b I'm curious if chemistry agrees?

 

[Randy Holmes-Farley]

Chemistry never disagrees with math, but it needs to be the right math.

 

[reggaedrummin]

(0.66 x 1) + (0.34 x 1.0264) = 1.008976

 

[psirex]

^ yep weighted avg

 

[Randy Holmes-Farley]

Yes, well, all my blabbering and you guys are exactly right. The chemistry does agree with the math, and you had the right math.

The answer is..... B. Mixing 66% pure fresh water with 34% seawater (sg = 1.0264)

Mixing 0.34 parts of water with a sg of 1.0264 and 0.66 parts of water with a sg of 1.0000 yields a sg of 0.34 x 1.0264 + 0.66 x 1.0000 = 1.0090

So, if you intend to treat a fish with hyposalinity, make up a solution of about 1 part tank water and 2 parts RO/DI, and then adjust a small amount from there, up or down, using more tnak water or Ro/DI water to get to 1.009.

 

[reggaedrummin]

Thanks!

 

[Randy Holmes-Farley]

Thanks!

You're welcome. Good job.

Happy Reefing.

 

[psirex]

I passed my first chemistry test!