If 38.5 mL of 8.9 ✕ 10-3 M HBr is added to 27.0 mL of 4.6 ✕ 10-3 M LiOH, what is the pH of the solution?
I got pH = 2.48 ... Please show some effort in solving problem.
The pH is 2.47. The above didn’t convert back to total molarity of the acid.
38.5-ml(8.9E-3M HBr) + 27.0-ml(4.6E-3M LiOH) => ?pH of final mix
=> 0.0385(8.9E-3)mole HBr + 0.027(4.6E-3)mole LiOH
=> (3.43E-4) mole HBr + (1.24E-4) mole LiOH
=> (2.188E-4) mole HBr (in excess)* + (1.24E-4) mole LiBr + (1.24E-4) mole H₂O
*LiOH is Limiting Reactant in the HBr + LiOH => LiBr + H₂O Rxn leaving HBr in excess.
[HBr] = 2.188E-4 mole HBr(aq)/(38.5+27.0)ml = (2.188E-4 mole HBr)/(0.0655-L soln) = 0.00334M HBr
LiBr ions do not hydrolyze in aqueous solution, therefore, the final mix pH is due to the 0.00334 M HBr that delivers 0.00334 M H⁺ ions as a strong acid ionizing 100%.
=> pH(final mix) = -log[H⁺] = -log(0.00334) = 2.476
To find the pH of the solution, we need to determine the concentration of the resulting solution after the HBr and LiOH react and determine if the solution is acidic, basic, or neutral. Here are the steps to find the pH:
1. Write a balanced chemical equation for the reaction between HBr and LiOH.
HBr + LiOH -> LiBr + H2O
2. Determine the limiting reactant.
To determine the limiting reactant, compare the moles of each reactant. You can find the moles by multiplying the volume (in liters) by the molarity of each solution:
Moles of HBr = 38.5 mL * (8.9 * 10^-3 M / 1000 mL)
Moles of LiOH = 27.0 mL * (4.6 * 10^-3 M / 1000 mL)
Compare the moles of HBr and LiOH to determine the limiting reactant.
3. Calculate the number of moles reacted based on the stoichiometry of the balanced equation.
The balanced equation shows a 1:1 ratio between HBr and LiOH. So, the moles of the limiting reactant will also be the moles of the product.
4. Calculate the concentration of the resulting solution.
To find the concentration of the resulting solution, you need to divide the moles of the product by the total volume of the resulting solution in liters (sum of the initial volumes of HBr and LiOH).
5. Determine the nature of the resulting solution.
If the resulting solution has an excess of H3O+ ions, it is acidic. If it has an excess of OH- ions, it is basic. If it has neither excess, it is neutral.
6. Calculate the pH of the solution.
If the resulting solution is acidic, you can use the formula pH = -log[H3O+]. If it is basic, you can use the formula pOH = -log[OH-] and then convert it to pH using the equation pH = 14 - pOH. If it is neutral, the pH will be 7.
Follow these steps to find the pH of the solution after the reaction.