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

The pH of the solution is 3.

Step-by-step 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=(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.