Chemical Mixture Problems

R

Richay

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Joined
Mar 31, 2006
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Hello, i've been having trouble with this for a while now.

Here's a problem I've completed of chemical mixture problems.

1 solution was 5% bromide and the other was 40% bromide, How much of each should be used to get 60 ml of a solution that is 12% bromide?

Answer in the form: 5% = ?, 40% = ?

Here's my steps.

(5)(S1) + (40)(82) = 720
300 - 5S + 405 = 720
300 + 35S = 720
35S = 420

S1 + S2 = 60

S1=48 S2=12

Oh well, my steps look weird but I cant include some of the numbers in the steps because I can only write them on paper and not type them. Blah, blah, blah, but you understand what i'm showing i hope.

And the answer is: 5% = 48, 40% = 12

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Although I got that problem correct (As my advisor said), I cannot figure out this one.

Lisa was in the next room and she needed 150 ml of a solution that was 30% glycerine. The two solutions available were 10% glycerine and 40% glycerine. How many milliliters of each should Lisa use?

Answer in the form: 10% = ?, 40% = ?

This one seems easier, but i'm making no progess. Help please...!
 
-------------------------------------------------------------------

Although I got that problem correct (As my advisor said), I cannot figure out this one.

Lisa was in the next room and she needed 150 ml of a solution that was 30% glycerine. The two solutions available were 10% glycerine and 40% glycerine. How many milliliters of each should Lisa use?

Answer in the form: 10% = ?, 40% = ?

This one seems easier, but i'm making no progess. Help please...!
Click to expand...

This problem is essentially the same as the other.

Try it this way:

Let x=amount of 10% solution
Then y=150-x=the amount of 40% solution.

\(\displaystyle .10x+.40(150-x)=.30(150)\)

Solve for x.
 
Remember this:

a @ x
b @ y
======
a+b @ z

(ax + by) / (a + b) = z
 
Thanks for the equation.
I'm kinda confused though.

Man this stuff really makes no sense to me.

I got like 3 different answers.

This is where I got confused. When it says ".10x" do I take x and multiply it by 10%? Or what? I don't understand what i'm doing.
But if that's the correct way....

x = 50

50 x 10% = 5

(150 - 50 = 100) So 100 x 40% = 40

5 + 40 = 45

150 x 30% = 45.

45 = 45

I'll show you the equation in an easier way to view.
.10x50 = 5 + .40x(100) = 40
So 40+5=45
And .30x150=45
45=45

10%=5
40%=40


As you guys can see, i am totally confused.
 
you ARE confused, Richay :shock:

.10x + .40(150 - x) = .30(150)
do the multiplications:
.10x + 60 - .40x = 45
still with me?
-.30x = -15
x = -15 / -.30
x = 50

Now to check:
.10(50) + .40(150 - 50) = .30(150)
5 + .40(100) = 45
5 + 40 = 45
45 = 45

WHY were you confused :?:
 
Well, I found out that x=50 and that both final solutions had to be 45.

I just did it in a weird way, lol.

I understand though.
But what does 40% and 10% in the end?

(Thanks for the help)
 
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