Question

How many litres of a $ 90\% $ acid solution must be added to $ 6 $ litres of a $ 15\% $ acid solution to obtain a $ 40\% $ acid solution?

Answer 1

Hint: Any solution with a higher concentration of hydrogen ions than water is classified as acidic; solutions with a lower concentration of hydrogen ions than water is classified as basic or alkaline. All acidic solutions have pH less than $ 7 $ ,while bases have pH more than $ 7 $ . Acidity is measured on a scale known as pH, which sets water at $ 7 $ .

Complete answer:
Let the amount of litres of $ 90\% $ acid solution be $ x $ .
From the question we know that the final solution will have $ 40\% $ acid solution and will be $ 6 + x $ litres in volume.
Multiplying the volumes by solutions, where the percentage of acid concentration is in decimal form.
 $ 0.9x + 0.15 \times 6 = 0.4 \times 6 + x $
Now after rearranging we get,
 $ 0.9x + 0.9 = 2.4 + 0.4x $
 $ 0.9x - 0.4x = 2.4 - 0.9 $
 $ 0.5x = 1.5 $
 $ x = \dfrac{{1.5}}{{0.5}} $
 $ x \Rightarrow 3 $
Hence, $ 3 $ litres of $ 90\% $ acid solution must be added to $ 6 $ litres of a $ 15\% $ acid solution to obtain a $ 40\% $ acid solution.

Additional Information:
The negative logarithm of $ {H^ + } $ ion concentration is used to calculate pH. As a result, the meaning of pH is justified as hydrogen power.

Note:
One of two methods is typically used to create acid solutions. One method is to dissolve a solid compound, such as citric acid, in water. The other method is to bubble gases through water, such as carbon dioxide (or $ HCl $ ). The material that dissolves in water is known as the solute in either case. The solvent is the liquid that dissolves the solute.