Question

A sample of 0.0020 mole of HCL is dissolved in water to make 2000 mL solution. What is the molarity of HCL solution, the H3O+, and the pH?

Answer 1

Answer:

The pH of the solution is 3.

Explanation:

Moles of HCl = 0.0020 mol

Volume of the solution = 2000 mL = 2 L

1 L = 1000 mL

Molarity = $\frac{\text{Moles of compound}}{\text{Volume of the solution (L)}}$

$M=\frac{0.0020 mol}{2 L}=0.0010 mol/L$

$HCl+H_2O\rightarrow H_3O^++Cl^-$

1 mol of HCl forms 1 mole of hydronium ion and 1 mol of chloride ions.

Then 0.0010 M of of HCl forms 0.0010 M of hydronium ion

The molarity of hydronium ion = 0.0010 M

The pH of the solution is defined as negative logarithm of hydronium ion or hydrogen ion concentration in a solution.

$pH=-\log[H_3O^+]$

$pH=-\log[0.0010 M]=3$

The pH of the solution is 3.

Answer 2

The molarity of HCL is 71mL, the H3O+ 49g, and the pH is 12.