suppose the student has only pure acid and 5% of acid. how much pure acid should be added to 5% acid to get 12ml of 10% acid.

Question

suppose the student has only pure acid and 5% of acid. how much pure acid should be added to 5% acid to get 12ml of 10% acid.

Answer 1

Pure acid is 100%.  We will say that is beaker X.  Beaker Y is 5%. We do not know how much is in each beaker.  After we dump the beakers together our final amount will be 12ml.  The amount in beaker X is x ml and the amount in beaker Y is y ml. 

 

 

We will have 2 equations.  An amount equation and an acid equation.

Amount equation:  x + y = 12

 

Acid equation:  100%x + 5%y = 10%(12ml)  ----->    1.0x + 0.05y = 0.1(12) ---> x + 0.05y = 1.2

 

Use substitution or elimination:

 

y = 12 - x    <------ came from amount equation

 

substitute into acid equation:    x + 0.05(12 - x) = 1.2   ---->  1x + 0.6 - 0.05x = 1.2

 

0.95x = 0.6

 

x = .63ml