Respuesta :
Answer: The teacher will need 14 ml of the 5% solution and 28 ml of the 65% solution.
Step-by-step explanation:
Since we have given that
There has a supply of 5% hydrochloric acid and a supply of 65% of hydrocholric acid.
The teacher needs to mix together to get 42 ml of 45% of hydrochloric acid for an experiment.
So, we will use "Mixture Allegation" to find the quantity of each solution,
Ist type of supply of HCL Â Â Â Â Â Â Â Â IInd type of supply of HCL
     5%                                65%
                         45%
----------------------------------------------------------------------------------------------
   65%-45%                  :            45%-5%
    20%                     :              40%
     2                      :              4
     1                       :               2
So, there is total quantity of mixture = 42 ml
So, Quantity of 5% solution will be
[tex]\frac{1}{3}\times 42=14\ ml[/tex]
Quantity of 65% solution will be
[tex]\frac{2}{3}\times 42=28\ ml[/tex]
Hence, the teacher will need 14 ml of the 5% solution and 28 ml of the 65% solution.