- 3 Look Up The Ph Ranges For The Acid Base Indicators That You Used Today Based On Those Ranges Which Would You Recomm 1 (13.16 KiB) Viewed 34 times
- 3 Look Up The Ph Ranges For The Acid Base Indicators That You Used Today Based On Those Ranges Which Would You Recomm 2 (47.75 KiB) Viewed 34 times
- 3 Look Up The Ph Ranges For The Acid Base Indicators That You Used Today Based On Those Ranges Which Would You Recomm 3 (77 KiB) Viewed 34 times
Molarity of unknown acid 1.00 M Molarity of NaOH OSM Solution # Volume of weak acid, mL Final Buret Reading, mL Initial Buret Reading, mL Volume of NaOH added in this Trial, mL Total Volume of NaOH in flask, mL Total Solution Volume, mL Initial Number of Moles HA Initial Number of Moles OH- Number of Moles HA after 1 40.00 Neutralization Number of Moles OH- after 12.50 mL 0.15mL 12.50 mL 1250 mL pH Color with Indicator Neutralization Reaction: 5250ML 4.00 Orange 004 moles 0.00625 0.03375 Neutralization Number of Moles A- after 0.00625 neutralization Equilibrium Reaction: 40.00 25.00 mL 12.50 m2 12:50ML 25.00 mL 65.00 mL 4.43 yellow 0.04 moles 0.0125 -0275 3 40.00 0.0125 HA + OH → H₂O + A= 37.50 mL 1250 mL 37.50ML Name: 25.00mL 0.04 moles - 01875 - 02125 O 01875 HA + H₂O = A + H₂O* 77.50-L 90.00m² 4.70 5.01 light yellow lighter yellow 4 40.00 C0435 025 CHAD 50.00-0 3750-L 12:50ML 50.00 ML 0.04 moles .025 .015 nizati
The object of this experiment is to measure the equilibrium concentrations s the equilibrium concentrations for all of the aqueous species in the acid ioniza order to calculate K. Looking at the ICE chart, a measurement of the Ho to calculate the K, values in the "Strong and Weak Acid" lab.) pH = -log [H₂O1] One method to find [H,O'] is to measure the pH of the acid solution. By measuring the pH, it is possible to calculate the equilibrium concentrations in weak a successive partial neutralizations. This is the data needed to calculate K. the initial concentration of [HA] and the equilibrium concentration of [HA] Similarly IA-I at the end of the acid, that at equilibrium "initial concentration-x" is approximately the same as the initial Note that for a weak acid, the amount of ionization is usually so small compared to the concentr concentration. With this in mind we will assume in our lab that [HA] at the end of neutralization s neutralization will equal the initial and the equilibrium concentrations of [A-]. An additional way to calculate K, relies on the fact that a partially neutralized solution is similar to a buffer solution. Buffer solutions can be analyzed using the Henderson-Hasselbach equation. It is derived from the equilibrium constant expression. This equation is only useful if K, is very small compared to the initial concentration of the weak acid. pH=pKa + log [A-[HA] (Henderson-Hasselbach equation) where pH = -log [H;0'], pKa = -log K₁. [A-] is the molarity of conjugate base at equilibrium, and [HA] is the molarity of weak acid at equilibrium. This equation can be evaluated like an equation of the line y = mx + b. By graphing pH vs. log [A-]/[HA] the y-intercept of a best fit line for the graph will be pk. K. can be easily found from this. Procedure 1. Obtain a 600-ml beaker. Label it Waste weak acid and NaOH". 2. Obtain 75 mL of a 0.5 M NaOH solution in a 150-ml beaker. Label the beaker with "NaOH" and its actual molarity. Condition and fill a buret with the NaOH solution. Label the buret. 3. Obtain 55 mL of 1.00 M unknown acid in a clean, dry 100 mL beaker. Label the beaker with "unknown acid". Condition a 20-mL volumetric pipette with the acid solution. 4. Prepare solution 1 by adding 40.00 mL of the unknown acid to a clean 250-ml volumetric flask. Then, add 12.50 mL of NaOH from the buret to the same flask. Record the exact volume of NaOH added on the Data Sheet. For color, you can add 10-15 drops of one of these acid base indicators: bromophenyl blue (pH range 3-4.6), methyl orange (pH range 3.1-4.4) or methyl red (pH range 4.2-6.3). Add Di water to the base of the flask neck and invert ten times to mix. Then, finish the solution, by adding DI water to the 250 mL mark on the flask and mix again. Si Obtain a pH meter and calibrate it with prepared buffer solutions. Do not leave the pH meter electrode tip out of liquid unnecessarily. au Quest or graphing calculator in utain the equation After F10 6. Pour the entire 250 mL solution 1 into a clean, dry 400-ml beaker containing a magnetic stir bar. Place the beaker on a stir plate and set stirring at a gentle to moderate pace. Place the pH meter in this