Question

You wish to determine the basicity of a cleaning product, but you have a problem---You can only use a standardized base in your buret! There's no way to neutralize a base with another base, but your lab partner approaches you with an idea. They have exactly 25.00 mL of 0.113 M HCl that they are willing to part with. You have 15.00 mL of your household cleaner (which is a basic solution). You add the entire 25.00 mL of HCl solution, and then add your indicator. You then begin to titrate the solution with your standardized NaOH solution. After you have added 18.20 mL of 0.103 M NaOH, the solution changes color and the excess acid has been neutralized. Based on this information, what is the concentration of base in the cleaning solution, and what is its pH (assuming it is a strong base)?

Answer 1

Here we use the following formula's:-

1. Molarity of acid * Volume of acid = Molarity of base * Volume of base

2. pOH = - log[OH^-]

3. pH + pOH = 14

Page L 0 Molarity of Hel (Mi) = 0.11BM Molarity of Nooh used for titration (M2) = 0.1039 Volume of All solution added (V) = 25.00 mL volume of NaOH solution used in titeation (V2) = 18.2mL. Volume of cleaning solution ou base (V3) = 15.00 m2 To calculate :- Concentration of Base (MB) = ? pH of lease ? Calculation: Here first we calculate volume of He solution used in titration ie V4. He us NaOH. MIVU = M2 V2 0.113 x V4 = 0.1038 1812 Vy = 0.103 x 18.2 - 1.8746 excess 0.113 0.113 TV4 = 16.58 m L volume of the that reacts with base = Total volume of tee - Excess Hel (vu) Q5 -16.58 VG = IV = 8.42mL.

Page 2 For Concentration of Base :- HR vs Malarity of Hel x volume of He reacts rolth base Base Molarity of & volume = Bose Base 0 (vs) Mi XVS = M₃ x V3 0.113 x 8.42 = M3 X8815 N3 = 0.113x8.42 = 0.95146 Mz = 0.0634M. Molarity of Base = Molanity of 2017 in base = Concentration of [oH] Therefore, conc. of Loh} - 0.0634 þOH = -lop [04] = -lof S000634 =-(-1.197) IPOH = log 1.1977 309 PH+ pot = 14 PH= 14-POH = 14-1.197 IPH-120807 Ang Concentration of = 0.0634M base in the cleaning and pH is 12.8. solution (M3).