Question

5. Will the calculated molarity of NaOH be lower or higher if you use tap water rather than deionized water to dissolve the KHP crystals or to rinse down the walls of the flask during the titration? Tap water contains some calcium bicarbonate. The calculated molti O NAOH will be lower lose top water rother thon deionited water to dissolve the crystals 6. Write and balance the equation for a neutralization of a sulfuric acid solution of unknown concentration by sodium hydroxide. 7. Calculate the molarity of an unknown sulfuric acid solution if a 25.0 mL sample of the acid solution consumes 27.2 mL of 0.138 M NaOH solution in a titration. 121

Answer 1

6. The balanced equation for the reaction between H2SO4 and NaOH is --> Na2SO4 (aq) + 2 H20 () H2SO4 (aq)2 NaOH (aq) 7 Number of moles of NaOH M*V= 0.138 M * 27.2 mL 3.7536 mmol Accordingto balanced equation, 2 moles of NaOH reacts with 1 mole of H2SO4 So, 3.7536 mmol of NaOH would react with 3.7536 mmol* 2 = 1.8768 mmol of H2SO4 Number of moles of H2SO4 1.8768 mmol Volume of H2SO4 = 25.0 mL Molarity of H2SO4 = moles/volume 1.8768 mmol/25.0 mL 0.075072 M Molarity of H2SO4 = 0.0751 M