Chemisty or math wizzes need to find an answer

[VAreef]

I over salted my change out water. I now have 8 gallons of water at 1.028 spec grav.

I'm trying to use the concentration equation but am stuck on how to find Volume to be added

C = concentration V = volume a=added i=initial f=final

Cf(Vf) = Ci(Vi) + Ca(Va)

1.024(Vf) = 1.028(8gal) + 1.000(Va)

It's been 20 years since I had to try and figure something like this out. It kinda reminds me of calculus a little. If I remember right do I have to make Vf equal to Vi+Va? then solve for Va? or something like that?

 

[Reefrookie]

Here's my formula..... Take a gallon out and replace with ro and retest :D

 

[VAreef]

Thank god my middle son is an honor roll student and wants to be a marine biologist. 1.33 gal of RO. I tested with about 1.5 that I had made while trying to figure out how much to make and it came out great just below 1.024. If I had added 1.33 exact it prolly woulda been 1.024 exact.

 

[Rcpilot]

Here's my formula..... Take a gallon out and replace with ro and retest :D

Thats the same formula I use! :Cheers:

 

[bjohanson1234]

Cf(Vf) = Ci(Vi) + Ca(Va)

1.024(Vf) = 1.028(8gal) + 1.000(Va)

The way you have it there, you would never figure it out since you have one equation and two variables.
To fix that, you need to make a new equation for Vf

Vf = 8gal + Va

Substitute out the Vf in the origianal equation and you get

1.024(8gal + Va) = 1.028(8gal) + Va

Then solve for Va
1.024(8gal) + 1.024(Va) = 1.028(8gal) + Va

1.024(VA) - Va = 1.028(8gal) - 1.024(8gal)

.024(Va) = .004(8gal)

Va = .004/.024(8gal)

Va = 1/6(8gal)

Va = 1.33gal

Sounds like your son did a good job.:Cheers:

 

[VAreef]

thats exactly how he did it BJ. He better make good grades in college too as I need him to support me when I am old.

 

[SaltwaterNoob17]

Math Memories. Sigh. Good 'Ol Substitution Property. ;)

 

[banthonyb71]

Here's my formula..... Take a gallon out and replace with ro and retest :D

Thats the same formula I use! :Cheers:

I think I like this formula alot better also.:smile:

 

[wontonflip]

Cf(Vf) = Ci(Vi) + Ca(Va)

1.024(Vf) = 1.028(8gal) + 1.000(Va)

The way you have it there, you would never figure it out since you have one equation and two variables.
To fix that, you need to make a new equation for Vf

Vf = 8gal + Va

Substitute out the Vf in the origianal equation and you get

1.024(8gal + Va) = 1.028(8gal) + Va

Then solve for Va
1.024(8gal) + 1.024(Va) = 1.028(8gal) + Va

1.024(VA) - Va = 1.028(8gal) - 1.024(8gal)

.024(Va) = .004(8gal)

Va = .004/.024(8gal)

Va = 1/6(8gal)

Va = 1.33gal

Sounds like your son did a good job.:Cheers:

My head hurts! :frustrat:
:mrgreen:

thats exactly how he did it BJ. He better make good grades in college too as I need him to support me when I am old.

Or at least, to support your reefing habit ;)

 

[sen5241b]

Cf(Vf) = Ci(Vi) + Ca(Va)

1.024(Vf) = 1.028(8gal) + 1.000(Va)

The way you have it there, you would never figure it out since you have one equation and two variables.
To fix that, you need to make a new equation for Vf

Vf = 8gal + Va

Substitute out the Vf in the origianal equation and you get

1.024(8gal + Va) = 1.028(8gal) + Va

Then solve for Va
1.024(8gal) + 1.024(Va) = 1.028(8gal) + Va

1.024(VA) - Va = 1.028(8gal) - 1.024(8gal)

.024(Va) = .004(8gal)

Va = .004/.024(8gal)

Va = 1/6(8gal)

Va = 1.33gal

Sounds like your son did a good job.:Cheers:

huh? .

 

[dcantucson]

My head hurts! :frustrat:

Mine too! What the heck are they discussing? :shock:

 

[bjohanson1234]

How to figure out how much water to add if you accidentally add too much salt and have a salinity that is too high.

 

[dcantucson]

It's easy! Not rocket science. Just add more RODI water!!! :lol: :mrgreen:

 

[VAreef]

I ran out of salt so needed to make sure it was right since I would have no way to correct it if I added to much RO. Plus sometimes it's just fun to figure stuff like that out. I think I'm going to use that same equation to figure out how much water I need to change out to get my nitrates down from 20ppm to 5ppm

 

[Bifferwine]

I think I'm going to use that same equation to figure out how much water I need to change out to get my nitrates down from 20ppm to 5ppm

You don't need a formula for that. It's 75%.

 

[VAreef]

You don't need a formula for that. It's 75%.

Oh great just ruin my fun I can't figure it out now since you gave me the answer LOL. Sometimes the common sense does evade me.

 

[Reefrookie]

That's called over engineering, we all have our moments ;-)

 

[VAreef]

AHA I found a good use for it. My tank was at 1.023 salinity with around 90gal total water volume. I figured that with a 10 gal water change I would need a salinity of 1.032 to increase my tank salinity to 1.024. OOOOO yeah and you guys made fun of me and my equation :D

 

[bjohanson1234]

I sure didnt. I find that kind of thing facinating:mrgreen: