SOLUTION: In your chemistry class, you are given a bottle of 5% acid solution and a bottle of 2% acid solution. You need 60 mL of a 3% solution for an experiment. How much of each solution

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Question 1097016: In your chemistry class, you are given a bottle of 5% acid solution and a bottle of 2% acid solution. You need 60 mL of a 3% solution for an experiment. How much of each solution do you need to mix together to get the desired concentration?
Found 2 solutions by jorel1380, josmiceli:
Answer by jorel1380(3719) About Me  (Show Source):
You can put this solution on YOUR website!
Let n and 60-n be the amounts of 5% solution and 2% solution needed, respectively. Then:
.05n+.02(60-n)=.03(60)
Solve for n
☺☺☺☺

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = mL of 5% solution needed
Let +b+ = mL of 2% solution needed
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(1) +a+%2B+b+=+60+ mL
(2) +%28+.05a+%2B+.02b+%29+%2F+60+=+.03+
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(2) +.05a+%2B+.02b+=+.03%2A60+
(2) +.05a+%2B+.02b+=+1.8+
(2) +5a+%2B+2b+=+180+
--------------------------------
Multiply both sides of (1) by +2+
and subtract (1) from (2)
(2) +5a+%2B+2b+=+180+
(1) +-2a+-+2b+=+-120+
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+3a+=+60+
+a+=+20+
and
(1) +20+%2B+b+=+60+
(1) +b+=+40+
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20 mL of 5% solution are needed
40 mL of 2% solution are needed
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check:
(2) +%28+.05a+%2B+.02b+%29+%2F+60+=+.03+
(2) +%28+.05%2A20+%2B+.02%2A40+%29+%2F+60+=+.03+
(2) +%28+1+%2B+.8+%29+%2F+60+=+.03+
(2) +1.8+=+.03%2A60+
(2) +1.8+=+1.8+
OK