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# A chemist has one 30-L bottle of 15% hydrochloric acid and one 30-L bottle of 90% hydrochloric acid. She mixes 20 L of 60% hydrochloric acid

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A chemist has one 30-L bottle of 15% hydrochloric acid and one 30-L bottle of 90% hydrochloric acid. She mixes 20 L of 60% hydrochloric acid and then pours 5 L of that solution back into the bottle containing the 90% hydrochloric acid. How strong is the acid in that bottle now?

Guest Feb 18, 2015

#2
+91915
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Well i don't usually make the same assumptions as Chris makes.

the 15% bottle is not used so it is irrelevant.

I am going to assume that the bottle containing the 90% concentrate is completely full. When the chemist tries to pour more acid into that bottle it cannot go in because the bottle is already full.

So the concentrate remains at 90% and the Chemist has to go to hospital to get his burns treated.  (yes it is bound to be a male, I expect that there are more male chemists in the world than female so I expect that statistically my bias would prove to be somewhat justified - sorry guys)

This is why chemists should never drink on the job!

Melody  Feb 18, 2015
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#1
+83944
+5

I assume that the chemist is mixing the first two to get the 20L of 60% solution.....we need to find out how many L of each of the first two must be combined to produce such a mixture.

So we have

.15x + .90(20-x) = 20(.60)

.15x + 18 - .90x = 12   simplify

6 = .75x   → x = 8 L of 15% solution

So (20-8) = 12 L of the 90% solution were used

Now......5L of this is poured back into the the bottle of 90% solution that now contains (30 - 12) = 18L

So we have

5L of 60% HCL = 3 L of HCL  ...  and 18L of 90% HCL  = 16.2 L of HCL

Then

(3 + 16.2) L of HCL / ( 5+ 18) total L of solution  = about an 83.5% concentration of HCL....

CPhill  Feb 18, 2015
#2
+91915
+5

Well i don't usually make the same assumptions as Chris makes.

the 15% bottle is not used so it is irrelevant.

I am going to assume that the bottle containing the 90% concentrate is completely full. When the chemist tries to pour more acid into that bottle it cannot go in because the bottle is already full.

So the concentrate remains at 90% and the Chemist has to go to hospital to get his burns treated.  (yes it is bound to be a male, I expect that there are more male chemists in the world than female so I expect that statistically my bias would prove to be somewhat justified - sorry guys)

This is why chemists should never drink on the job!

Melody  Feb 18, 2015
#3
+1037
0

Melody just passed her Professional Troll certification test.

Even if is the bottle wasn’t full, pouring a dilute solution into a highly concentrated reactive solution is indicative of a raging case of CDD!

Nauseated  Feb 18, 2015
#4
+91915
0

Thanks, .... I think.

It has been my lifes ambition to be a Professional Troll.     LOL

Melody  Feb 18, 2015
#5
+83944
0

I see that Melody and Nauseated have avoided the "acidic" nature of this question.....

But....that doesn't mean they have necessarily avoided drinking the Kool-Aid.......

CPhill  Feb 18, 2015
#6
+91915
0

you are right Chris,

I can at time be difficult to avoid Kool-Aid

Melody  Feb 19, 2015

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