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### Topic: Can sb explain me how can this be solved?  (Read 1065 times)

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##### Can sb explain me how can this be solved?
« on: October 14, 2019, 04:49:58 AM »
I don t know where to post it ,i posted it on undergrad here too
Can sb explain  to me please? ...
What is the ratio two solutions of H2SO34 have to be mixed in order to result a 20 percent H2SO4 solution
The two solutions are
2.06M with a density 1.125 grams per ml H2SO4
2.a solution with 25 percent concentration and density  1.176g per ml.What i mean by ratio is for ÷exmple 1:2
M means mass,C means concentration in percent
FP means final percent = 20
C1 =  you don t have it i  the problem
C2 equals  25 percent
I tried to solve it by a formule M1/M2=C2-FC/FC-C1
Tried to find the percent mass ... but in vain
« Last Edit: October 14, 2019, 05:01:48 AM by Romenumeral »

#### mjc123

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##### Re: Can sb explain me how can this be solved?
« Reply #1 on: October 14, 2019, 06:18:29 AM »
Quote
C1 =  you don t have it i  the problem
Yes you do. 1L of solution weighs 1125 g and contains 2.06 moles of H2SO4. What is the mass of H2SO4, and what is the % concentration?
Suppose you have 100 g of solution, made up from x g of solution 1, concentration C1, and 100-x g of solution 2, concentration C2.
What is the concentration of the combined solution, in terms of x? What value of x is needed to make this concentration equal to 20%?
What is the ratio of solution 1 to solution 2?

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##### Re: Can sb explain me how can this be solved?
« Reply #2 on: October 14, 2019, 07:32:07 AM »
Nope ,that was an example of how the answer looks... i said it isn t given as in you have to find the concentration

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##### Re: Can sb explain me how can this be solved?
« Reply #3 on: October 14, 2019, 07:45:09 AM »
So,what " you" have to find is  what is the ratio the two solutions of H2SO4  have to be mixed  in order to result  a 20 percent concentration H2SO4

And related to what you said about knowing the concentration percent of first solution .C% of first solution=dissolved mass of H2SO4 2.06 moles (202.72grams).I get what you did there multiplied the volume 1L with density and got 1125grams solution.So C% of the first solution is =202.72 g/1125 grams dissolved solutions multiplied by 100 ?That gives 18 percent...or 18.02

#### chenbeier

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##### Re: Can sb explain me how can this be solved?
« Reply #4 on: October 14, 2019, 07:50:03 AM »
Next step use cross rule.
You have two solution with the kown Percentage and also the new percentage after mixing.

Calculate the weight parts now.

Do you know how to do?

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##### Re: Can sb explain me how can this be solved?
« Reply #5 on: October 14, 2019, 07:54:42 AM »
Next step use cross rule.
You have two solution with the kown Percentage and also the new percentage after mixing.

Calculate the weight parts now.

Do you know how to do?
So C% of the first solution is =202.72 g/1125 grams dissolved solutions multiplied by 100 ? i did that part right ...you have to divide it by 1125 grams? I m trying now what you said..

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##### Re: Can sb explain me how can this be solved?
« Reply #6 on: October 14, 2019, 08:11:59 AM »
Next step use cross rule.
You have two solution with the kown Percentage and also the new percentage after mixing.

Calculate the weight parts now.

Do you know how to do?
...Well since in the first solution you used mass of H2SO4 / total mass which was  1125 g ,isn t  1125g the mass of the first?

Now i have to find the total mass of the second solution..i don t know i m.stuck because to you is given only density and percent(25) and density 1.176 grams per ml....

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##### Re: Can sb explain me how can this be solved?
« Reply #7 on: October 14, 2019, 08:23:26 AM »
I solved it guys.thank you a lot,but  i still have to know the answer  to the previous reply.Thank you a lot.So about Concentration percent is there any problem if you have more than 100g where denominator is

#### chenbeier

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##### Re: Can sb explain me how can this be solved?
« Reply #8 on: October 14, 2019, 08:28:42 AM »
You dont show anything. What is the result how much of both solutions you have to mix in which ratio?

Show the cross rule. Start with the percentages on left side put in the middle the new percentage. What are the result of the weight parts.

« Last Edit: October 14, 2019, 08:45:53 AM by chenbeier »

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##### Re: Can sb explain me how can this be solved?
« Reply #9 on: October 14, 2019, 09:20:56 AM »
The result is 5:2 i really don t know wgat you mean by weight parts...
From formula that i wrote:
Ms1/ms2=c2-cf/cf-c1 resulted
1125/x=25-20/20-18 ..this is the answer i needee not mass of the secobd solution
But the mass of the second is
1125x2/5=.

#### chenbeier

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##### Re: Can sb explain me how can this be solved?
« Reply #10 on: October 14, 2019, 09:33:20 AM »
Yes 5:2 is correct. It means you have to mix 5 weight parts 18% with 2 weight parts 25% . The result is you get 7 weight parts 20%

.
Example you mix 1 kg 18% ( 5wp) with 0,4 kg 25 % (2 wp) give 1,4 kg 20% (7 wp)

With the densities you can also convert to volume, but the mixture has volume contraction. The sum is mostly not the same.

1 kg means 888 ml and 0,4 kg means 340 ml.

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##### Re: Can sb explain me how can this be solved?
« Reply #11 on: October 14, 2019, 10:24:30 AM »
1 kg 888ml,0.4 kg ..340ml i don t know where you get that from  i understand that you multiply with density from what you said but... what density?.As to "weight parts"i don t understand what you wanna say,i think that is cause english isn t my mother tongue, looked it up,the word,but i still don t know what it means.What you say by weight  parts is like dividing that 18 percent concentration in x "weight parts" of 18 percent concentration ...?

Or the full solution ,18 percent, 5 times?

Edit
I know now why is 5  ...times 18  because you cross multiply , but is it like you put that  solution 5 times..? Or ...
« Last Edit: October 14, 2019, 10:44:31 AM by Romenumeral »

#### chenbeier

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##### Re: Can sb explain me how can this be solved?
« Reply #12 on: October 14, 2019, 11:04:03 AM »
density = rho = m/V

V =m/rho, V = 1kg/1.125kg/l = 0,888 l

The cross rule works only with the mass or weight not with the volume.

Use weight parts or weight pieces.

18.         5 parts = 25 - 20

20

25          2 parts = 20 - 18
___________
7 parts = 5 + 2

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##### Re: Can sb explain me how can this be solved?
« Reply #13 on: October 14, 2019, 12:40:51 PM »
density = rho = m/V

V =m/rho, V = 1kg/1.125kg/l = 0,888 l

The cross rule works only with the mass or weight not with the volume.

Use weight parts or weight pieces.

18.         5 parts = 25 - 20

20

25          2 parts = 20 - 18
___________
7 parts = 5 + 2

Ok,thank you for everything i will certainly come back w problems that i don t understand,i swear this is the best chem forum