September 22, 2020, 08:03:54 AM
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### Topic: Dilute 20% solution to create 3 litres of 1% solution  (Read 332 times)

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#### saparama

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##### Dilute 20% solution to create 3 litres of 1% solution
« on: January 16, 2020, 02:58:15 PM »
The problem is: We have a 20% solution of NaCl and we want to create 3 litres of 1% NaCl solution. Question is how many litres of 20% solution and how many litres of water should we use to create such thing.

It was on my exam and I tried to use c1.V1 = c2.V2    From  equation m1.w1 = m2.w2 i found out that m1 = 0,05.m2  but that is all I got. Can someone please help me? How should I continue? Does this problem have a solution?
« Last Edit: January 16, 2020, 04:25:55 PM by saparama »

#### chenbeier

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##### Re: Dilute 20% solution to create 3 litres of 1% solution
« Reply #1 on: January 16, 2020, 04:10:27 PM »
Use cross rule

20.             1 weight part
1
0.               19 weight part
______________
20 weight part = 3 kg

You need the specific gravity to convert to volume.

If you calculate in mass 3 kg 1% solution  = 20 weight parts

You need 150 g 20% solution ( 1 weight part) and 2,85 kg (19 weight part) of water.

#### saparama

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##### Re: Dilute 20% solution to create 3 litres of 1% solution
« Reply #2 on: January 16, 2020, 04:18:01 PM »
Use cross rule

20.             1 weight part
1
0.               19 weight part
______________
20 weight part = 3 kg

You need the specific gravity to convert to volume.

If you calculate in mass 3 kg 1% solution  = 20 weight parts

You need 150 g 20% solution ( 1 weight part) and 2,85 kg (19 weight part) of water.

Thank you very much for you answer but I have a question. They wanted the answer in volumes. Can I use 0,150 litres and 2,85 litres?

#### Borek

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##### Re: Dilute 20% solution to create 3 litres of 1% solution
« Reply #3 on: January 16, 2020, 05:15:23 PM »
These will be only approximate, density of the 20% NaCl solution is around 1.15 g/mL, so 150 g is quite far from being 150 mL,

If you were not given densities 150 mL is your best bet though.
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