Question

What is the ph of a solution made by mixing 100.00 ml of 0.20 m hcl with 50.00 ml of 0.10 m hcl? assume that the volumes are additive?

Answer 1

I completely ignored sig figs though

Answer 2

Answer: The pH of the solution is 0.78

Explanation:

To calculate the molarity of the solution after mixing 2 solutions, we use the equation:

$M=\frac{n_1M_1V_1+n_2M_2V_2}{V_1+V_2}$

where,

$n_1,M_1\text{ and }V_1$ are the n-factor, molarity and volume of the HCl

$n_2,M_2\text{ and }V_2$ are the n-factor, molarity and volume of the HCl

We are given:

$n_1=1\\M_1=0.20M\\V_1=100.00mL\\n_2=1\\M_2=0.10\\V_2=50.0mL$  

Putting all the values in above equation, we get:

$M=\frac{(1\times 0.20\times 100)+(1\times 0.10\times 50.0)}{100.00+50.0}\\\\M=0.166M$

The concentration of $H^+$ ions in the resulting solution will be same as the molarity of solution which is 0.166 M.

pH is defined as negative logarithm of hydrogen ion concentration. It is basically defined as the power of hydrogen ions in a solution.

Mathematically,

$pH=-\log[H^+]$

We are given:

$[H^+]=0.166M$

Putting values in above equation, we get:

$pH=-\log(0.166)\\\\pH=0.78$

Hence, the pH of the solution is 0.78