Convert 65% solution to 35% ??

oldog

Member

• Jun 25, 2014

• #1

I googled this but got nothing but hard core chemistry formulas with
' moles ' etc . Can someone give me a simple way of making up say
500ml ( or a pint-16oz) of a 35% solution from a solution of 65 % concentration ?
How much water to add to how much of the 65% ?

Thanks lots !

 

I

Ickis

Active member

Veteran

• Jun 25, 2014

• #2

If you had 250 ml of 65% solution and added 250 ml of water you would have 500 ml of 32.5% solution.

So if you made a formula as such

250/500 = 32.5/65 so if you want 35% you use X/500=35/65 the slash means over so it is X over 500 and 35 over 65. Now cross multiply and you get X x 65 = 500 x 35

So X x 65 =17,500 so X= 17500 divided 65 so X=269.23

So take 269 ml of 65% solution and add 231 ml of water for 500 ml of 35% solution.

 

oldog

Member

• Jun 25, 2014

• #3

If I had a teacher like you when I was in school, I wouldnt
be here posting this. I am numerically handicapped.
Thanks !

 

I

Ickis

Active member

Veteran

• Jun 25, 2014

• #4

I used to try and solve every math question with ratios. It would drive my teachers nuts.

I am glad it helped you oldog.

 

dank.frank

ef.yu.se.ka.e.em

ICMag Donor

Veteran

• Jun 25, 2014

• #5

This is the actual formula for such:

Step 1:

Volume of stock needed = concentration desired / concentration of stock solution x total volume of solution

? = 0.35 / 0.65 x 500mL

? = 0.538 x 500mL

? = 269mL

This means you need 269mL of 65% stock concentration in 500mL of solution to have a 35% concentration.


Step 2:

Total volume of solution - stock solution needed to determine how much water should be present in a 35% solution:

500mL - 269mL = 231mL



dank.Frank

 

Last edited: Jun 25, 2014

I

Ickis

Active member

Veteran

• Jun 25, 2014

• #6

dank.frank said:

This is the actual formula for such:

Step 1:

Volume of stock needed = concentration desired / concentration of stock solution x total volume of solution

? = 0.35 / 0.65 x 500mL

? = 0.538 x 500mL

? = 269mL

This means you need 269mL of 65% stock solution in 500mL of solution to have a 35% concentration.


Step 2:

Subtract the amount of stock solution from the total volume to determine how much water should be present in a 35% solution:

500mL - 269mL = 231mL



dank.Frank

Click to expand...

Hey that is the same as mine. X/500=35/65 X= 35/65 x 500 which is .538 x 500 = 269 I was breaking it down and showing the ratio set-up.

That's what my teachers would do. LOL!

 

dank.frank

ef.yu.se.ka.e.em

ICMag Donor

Veteran

• Jun 25, 2014

• #7

Yeah, I just wanted to put the formula itself and the steps in play so people could see how to arrive at the answers you did...and where to plug what information.

Teach a man to fish...blah, blah, blah...



dank.Frank