Question

How many litres of a $90\mathrm{\%}$ acid solution must be added to $6$ litres of a $15\mathrm{\%}$ acid solution to obtain a $40\mathrm{\%}$ 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 $90\mathrm{\%}$ acid solution be $x$ .
From the question we know that the final solution will have $40\mathrm{\%}$ 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,
 $0.9x+0.9=2.4+0.4x$
 $0.9x-0.4x=2.4-0.9$
 $0.5x=1.5$
 $x={\displaystyle \frac{1.5}{0.5}}$
 $x\Rightarrow 3$
Hence, $3$ litres of $90\mathrm{\%}$ acid solution must be added to $6$ litres of a $15\mathrm{\%}$ acid solution to obtain a $40\mathrm{\%}$ 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.