Question
please just use dimensional analysis
ACID BASE TITRATIONS OBJECTIVES To learn general techniques generate a standardized To determine concentration of various acid samples SAFETY Goggles must be worn for the enti ab period even if you are done an apron your skin and clothi Sodium hydroxide is skin and eyes. Rinse off thoroughly with water Potassium may irritate lungs and mucous All solutions may be disposed of in the sink. INTRODUCTION Acid-base titrations make u of the general neutralization reac or concentrations of an acid base his n (acid ater) quantitate amounts experiment, a base added to a measured amount of acid An occurs at the equivalence point, when moles of base exactl acid indicato such as phenolphthalein, wil change color at the the acid is exactly neutralized. This neutral equal the moles of acid in the sample. equivalence point, indicating when the neutralization reaction is complete PROCEDURES WORK ALONE PART STANDARDIZATION oF A soDiu HYDRoxIDE soLuTION THE TITRANTn A. Pre the NaOH solution Weigh approxima tely 2 1 grams of NaoH pellets in a weighing dish (2.0 to 2.2 grams is acceptable) Carefully transfer all of the NaoH pellets (using a spatula nto a 250-mL Florence flask. Add approximately 100 mL deionized water and swirl the contents he s are completely dissolved 3. Add enough deionized water to fill the Florence flask to the bottom of the neck Rinse the storage bottle from your drawer with water and pour all of the NacH solution into the bottle. Cap the bottle mes. After this step, it is important not to add more water to this solution and invert it several You must use the same NaoH solution for the entire experiment (both days)--this is critical. You will lose significant points if you do not save your tirant (or if you cause another person to lose their titrant B. Dete the NaOH (e stand zation a Check for cleanliness by running water through Water should flow freely from the tip. If beads of water remain inside the burette, add soapy water clean with a burette brush 2. Rinse the burette twice with your NaoH solution (about 5 demonstrated by your instructor or each through the and then pour the rest out of the top 3. Set up a ring stand with clamp and attach the clean Lower the burette so that the top is below funnel to fill the burette to above the line with you NaOH solution. Remove the funnel. Drain the solution through the tip (be sure to flush out any bubbles in the until the bottom of the meniscus is at or below the zero line, Record the initial volume u of digits hundredth's place (potassium hydrogen phthalate, KHCeHeOM) on the analytical balance. Weigh out approximately 0.50 grams of KHP flask (clean and preferably dry), or Record all digits. the crystals directly into a tared into a flask dissolve the 6. weigh the crystals in a weighing boat and care transfer them of phenolphthalein indicator. Be sure to water droe Add about 25 mL of deoinized wat to the flask and add 2 drops solution with a little more first KHP-f any crystals are clinging to the walls of the flask, rinse them down into the is point which the 7. Use the demonstrated techniques to titrate the dissolved KHP endpoint, which final volume be sure to of titrant causes the solution to tum pink and stay pink for at least 30 seconds. the first trial, and line 8. steps 5-7 two more times trials total of nt used for the last have at least that volume remaining in the next trial. You must not drain the past the 9. excess NaOH solution back in your storage bottle, seal the bottle tightly, and st n the side bench) for day 2 of the experiment on
Explanation / Answer
1.
KHP(aq) + NaOH(aq) --> H2O(l) + KNap(aq)
or
KHC8H4O4(aq) + NaOH(aq) KNaC8H4O4(aq) + H2O(l)
2.
Total ionic:
C8H4O4- + K + H+ + Na+ + OH- ===> C8H4O4= + K+ + Na+ + H2O
Net ionic:
H+ + OH- ===> H2O
3. Trail 1
Moles of KHP = 0.5010 g/ 204.227g/mol
=2.453*10^-3 MOLES
KHP reacts with NaOH in 1:1 molar ratio
Molar mass KHP = 204.227g/mol
Volume NaOH used = 42.65mL
15.65 mL of NaOH solution contains 0.002453 mol NaOH
1000 mL NaOH solution contains : 0.002453 /15.65 *1000 = 0.156 M NaOH
. Trail 2
Moles of KHP = 0.5029 g/ 204.227g/mol
=2.5*10^-3 MOLES
KHP reacts with NaOH in 1:1 molar ratio
Molar mass KHP = 204.227g/mol
Volume NaOH used = 16.27mL
16.27 mL of NaOH solution contains 0.0025 mol NaOH
1000 mL NaOH solution contains : 0.0025 /16.27 *1000 = 0.151 M NaOH
. Trail 3
Moles of KHP = 0.5018 g/ 204.227g/mol
=2.46*10^-3 MOLES
KHP reacts with NaOH in 1:1 molar ratio
Molar mass KHP = 204.227g/mol
Volume NaOH used = 15.73 mL
15.73 mL of NaOH solution contains 0.00245 mol NaOH
1000 mL NaOH solution contains : 0.00245 /15.73 *1000 = 0.156 M NaOH
4.
Average molarity = [0.156 M NaOH+0.151 M NaOH
+0.156 M NaOH]/3
=0.154 M NaOH
