Question

Sodas are not only full of sugar (124 grams/L), but they are also acidic and will dissolve your teeth, composed of hydroxyapatite (Ca10(PO4)6(OH)2), in a short period of time. Strong acids completely dissociates when added to water. Hydrochloric acid (HCl) is a strong acid and when added to water will form H+ and Cl- . Calculate the pH of water after 1.5 mg of HCl is added to 354 mL of water (a 12 ounce can). Is this solution more or less acidic than the Pepsi in our example from class?

Answer 1

Answer:

The pH of the HCl solution is 3.9

Explanation:

Knowing the molar mass of HCl (36.5g/mol) it is possible to calculate the number of moles of HCl in the solution,

$\frac{1.5x10^{-3}g}{36.5g/mol} = 4.1x10^{-5}moles$ of HCl

HCl is a strong acid and when added to water will form H+ and Cl-, thus the moles of HCl are equal to moles of H+ in 354 mL of water

$\frac{4.1x10^{-5}moles }{354mL} x 1000= 1.16x10^{-4} M$

The concentration of protons in the solutions is $1.16x10^{-4} M$.

The expression used to calculate the pH is

$pH = -Log ([H^{+}]) = -Log (1.16x10^{-4} M) = 3.9$

Hence, the pH of the HCl solution is 3.9 and Pepsi has a pH of 3.4 approximately, so they have almost the same pH.