Question

65 g of hydrogen chloride (hcl) is dissolved in water to make 5.0 l of solution. what is the ph of the resulting hydrochloric acid solution?

Answer 1

65 grams of HCl = 65/36.5 moles of HCl = 1.78 moles
1.78 moles of HCl dissolved to make a 5 litres of solution has a concentration of 1.78/5 = 0.36 mol/dm^3 (Note: 1 litre = 1 cubic decimetre)

In a strong acid, such as HCl, [H+] = [acid], so [H+] = 0.36

To calculate pH, we have to take the negative logarithm of the concentration of protons

So, -log(0.36) = 0.45

Hope I helped!! xx