Calculate the pH of a solution containing 82.0 grams of HCl dissolved in 0.950 l

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Explanation / Answer

In order to calculate the pH of HCl, it is necessary to find thehydronium ion concentration H3O+. To begin, it is always a good idea to set up a balancedreaction: HCl (aq) + H2O (l) --> H3O+(aq) + Cl- (aq) Hydrochloric acid is dissolved in water to form hydronium ions andchloride ions. By setting up a balanced equation, it is observedthat for every one mole of HCl reacted, one moleH3O+ is produced. HCl is a strong acid. Therefore, it will dissociate completely inwater. This means that once the concentration of HCl is found, onealso knows the concentration of H3O+. Becauseit completely dissociates, and for every mole of HCl reacted, onemole of H3O+ is produced, the HClconcentration is equal to the H3O+concentration. This means it is necessary to find the HCl concentration. This canbe achieved by using the equation for molarity: Molarity=moles/liter If there are 82.0 grams HCl, using the molar mass of HCl will givehow many moles of HCl are present: Molar Mass= H: 1x1.01 + Cl=1x35.45                  = 1.01 + 35.45 = 36.46 g/mol Using this, the 82.0 g of HCl can be converted to moles: 82.0 g HCl x 1 molHCl      = X moles HCl                       36.46 g HCl Once X is calculated, the moles of HCl can be plugged into themolarity equation: Molarity of HCl= X mol HCl                            0.950 L This will give the concentration of the HCl, which is the same asthe concentration of the H3O+ ([H3O+]). In order to find the pH of this: pH = -log [H3O+]

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