Question

Page 12 of 12 BG10.2 Acid-Base Titration As part of a lab exam, your instructor gives you a sample of hydrochloric acid and asks you to determine its concentration using the procedure in this lab. You make up a solution of sodium hydroxide by dissolving 2.0 g of sodium hydroxide pellets in water and diluting it to exactly 500 mL You then titrate your sodium hydroxide solution three times with a hydrochloric acid solution with a molarity of 0.1024 molliter. You measure the volumes of reagents in the table below. Calculate the best estimate of the molarity of the sodium hydroxide solution and the relative deviation of the results. Trial mL of acid mL of Base Molarity of Base, Deviation from MOLL Average 25.89 23.23 0.14 0.596 27.43 24.93 0.087 0.14) 0.15 24.55 21.83 0.085 | Rel. Avg. oun Avg. 3086 Dev. 3. You now titrate the unknown hydrochloric acid solution with your sodium hydroxide solution which you standardized above. Use the molarity for the sodium hydroxide solution that you calculated in 2. Above to calculate the molarity of the acid solution. The volumes of reagents are shown in the table below. What is the best estimate of the concentration of the hydrochloric acid solution? What is the relative average deviation of your measurement of the hydrochloric acid solution? Molarity of Acid, Deviation from Trial mL of acid mL of Base Mol/L Average 24.73 29.86 27.21 33.20 22.44 26.69 Avg Rel. Avg Dev.

Answer 1

M_acid $\times$ V_acid = M_base $\times$ V_base

here the molarity (M) of the base = 0.114 M

Trial 1

Molarity of acid =( molarity of base $\times$ volume of base) / volume of acid

= ( 0.114 $\times$ 29.86) / 24.73

= 0.137 M

Trial 2

molarity of acid = ( 0.114 $\times$ 33.20) / 27.21

   = 0.139 M

Trial 3

Molarity of acid = ( 0.114 $\times$ 26.69) / 22.44

   = 0.135 M

Trial mL of acid mL of base Molarity of Acid (mol/L) Deviation from average 24.73 29.86 0.137 27.21 33.20 0.139 0.002 22.44 26.69 0.135 0.002 Avg. 0.137 Rel. Avg. Dev. 0.0013