- A strong acid is an acid that ionizes 100% in solution. Because that example, hydrochloricacid, HCl, together a strong acid it donates a proton come water, H2O, to kind the hydronium ion, H3O plus, and also the conjugate base to HCl i m sorry is the chloride anion, Cl minus. In reality, this reactionreaches an equilibrium. However, the equilibriumlies so much to the right and favors the product somuch that we don't draw an equilibrium arrow,we simply attract an arrowhead going come the right,indicating the reaction basically goes to completion. And if the reactionessentially goes come completion, we deserve to say that hydrochloricacid ionizes 100% and forms hydronium ionsand chloride anions. So basically there is no much more HCl left, it's every turned intoH3O plus and also Cl minus. It's likewise acceptable tocompletely leave water the end of the equation and toshow hydrochloric acid, HCl, turning into H plus and Cl minus. When again, since HCl is a solid acid, there's just an arrowhead going come the ideal indicating HCl ionizes 100%. And also since there's only onewater molecule difference in between H plus and H3Oplus, H plus and H3O to add are supplied interchangeably. Hydrochloric mountain is an example of a monoprotic solid acid. Monoprotic means, hydrochloricacid has actually one proton the it can donate in solution. Other examples of monoproticstrong acids include hydrobromic acid, HBr,hydroiodic acid, HI, nitric acid, HNO3, andperchloric acid, HClO4. Sulfuric mountain is H2SO4and it's a strong acid, however it's a diprotic acid,meaning it has two protons that it have the right to donate, however,only the an initial ionization because that sulfuric acid is strong. Let's calculation the pH ofa strong acid solution. In this case, we're gonnado a 0.040M solution of nitric acid. Nitric mountain is HNO3, andnitric mountain reacts through water to type hydronium, H3O plus,and nitrate, no3 minus, i m sorry is the conjugate base 2HNO3. Since nitric mountain is a solid acid, us assume the reaction goes come completion. Therefore, if the initialconcentration that nitric acid is 0.040M, looking in ~ our mole ratios in the well balanced equation,there's a one in front of nitric acid and also there's alsoa one in former of hydronium and a one in front of nitrate. Therefore, if the reactiongoes come completion, the concentration ofhydronium would also be 0.040M and also the exact same with the nitrate anion, that would additionally have aconcentration that 0.040M. Due to the fact that our goal is to calculatethe pH of this solution, we recognize that the equationfor pH is pH is equal to the an unfavorable log of theconcentration the hydronium ions. Therefore, we just need toplug in the concentration of hydronium ions right into our equation. This offers us the pH is same to the an adverse log the 0.040, i beg your pardon is same to 1.40. So even though this isa pretty dilute solution of nitric acid, becausenitric acid is a strong acid, the pH is nice low. Likewise note due to the fact that we havetwo significant figures because that the concentration the hydronium ions, we require two decimal placesfor our last answer. Let's do an additional problemwith a solid acid solution. Let's to speak we have 100 mlof one aqueous equipment of hydroiodic mountain andthe pH of the equipment is same to 1.50. And also our score is to find the massive of hi that's existing in solution. Hydroiodic mountain reacts withwater to kind the hydronium ion and also the iodide anion. And the mole ratio of HIto H3O to add is one-to-one. For this reason if we can discover theconcentration that hydronium ion and solution, the should additionally be the early stage concentrationof hydroiodic acid. And once we discover the early concentrationof hydroiodic acid, we can uncover the massive of hello that's present. Since we are given the pH in the problem, we have the right to plug that directlyinto our equation, which gives us 1.50 isequal to the an adverse log the the concentration of hydronium ions. To deal with for the concentrationof hydronium ions, us can first move the negativesign come the left side, which provides us negative1.50 is same to the log of the concentration that hydronium ions. And to remove the log,we have the right to take 10 come both sides. So the concentration that hydronium ion is same to 10 come the an adverse 1.50, i m sorry is equal to 0.032. So the concentration ofhydronium ions is 0.032M. And also because the mole ratioof hydronium ion to hi is one-to-one, the initialconcentration of hi is additionally 0.032M. Now that we know theinitial concentration that HI, we're ready to findthe massive of hello present. Molarity is moles every liter, for this reason let's go ahead and rewrite this as 0.032 moles per liter. The volume the the solutionis 100 milliliters, which is equal to 0.100 liters. So if us multiply molesper liter by the volume, i m sorry is 0.100 liters, literswill cancel and give united state moles. Therefore this is same to 0.0032 moles of HI.
Because our score is come findthe fixed of hi present, the last step is tomultiply the moles of hi by the molar mass which is 128 grams every one mole of HI. So most of HI would certainly cancel outand this gives us 0.41 grams as our last answer.