CHEM LAB 9

What is the approximate pH of a solution X that gives the following responses with the indicators shown? Indicators HIn → In- pH range Solution X methyl orange red-yellow 3.2-4.4 yellow methyl red red-yellow 4.8-6.0 yellow bromthymol blue yellow-blue 6.0-7.6 green phenolphthalein colorless-pink 8.2-10.0 colorless 8.2-10.0 3.2 -4.4 6.0 - 7.6 4.8 - 6.0

File Edit View Insert Format Tools Add-ons He Introduction Procedure Observation Observations: 100% 1 2 I 3 I 4 Initial solution temperature (°C): 20.8°C Maximum solution temperature (°C):27°C Recall that the steepest point on the pH curve occurs at the equivalence point, that is, when the acid is exactly neutralized. Total volume of NaOH titrated to reach end-point or neutralization (steepest point on the pH curve):25ml 14 13 Mass of solution (g) = (Volume of NaOH titrated (ml) + Volume of HCl (ml)) x density Mass of solution = 76 g 34 32 31 30 29 Note: Assume a density of 1.038 for both NaOH and HCI 11 10 pH Heat released by neutralization: 27 Q = mcAT Q = 1.9 x 10^3 J 25 where m is the mass solution in grams, c = specific heat capacity of our solution (=4.184 J/°C g) and AT=T, max 23 22 21 20 Tinitial- Heat of Neutralization = Q/moles of limiting reactant Q/moles of NaOH titrated at neutralization Q/(Molarity of NaOH x volume of NaOH (in litres)) 10 15 20 25 30 35 40 45 %3D Volume…

Interpret pH titration plots. Answer the following about the titration plot shown below, involving a monoprotic acid and base. 20 mL of 0.1M titrand titrated with 0.1M titrant. Data points at 1 mL increments. 14.0 12.0 10.0 5 8.0 6.0 4.0 2.0 0.0 seededood 0 0.0 10.0 مهمه 20.0 30.0 Volume of titrant (mL) (a) Is the species being titrated an acid or a base? (b) Is the species being titrated strong or weak? (c) What is the value of Ka (if a weak acid) or K, (if a weak base) for the species being titrated? If the species is strong (100% dissociated), enter 999. rààààààààà 40.0 50.0

If the equivalence point of the titration is when the pH is 4, what indicators could you use? Acidic Basic T Indicator pH Range 2 3 4 5 6 7 8 9 10 11 12 13 14 Thymol Blue 1.2-2.8 and 8.0-9.2 Methyl Orange 3.0-4.4 Bromphenol Blue 3.0-46 Congo Red 3.0-5.0 Bromcresol Green 38-5.4 Methyl Red 4.4-6.2 Bromthymol Blue 60-7.6 Phenol Red 6.8-8.4 Which one would you use if the pH is 6?

A solution has a pH of 4.5. What would be the color of the solution if each of the following indicators were added? (See the figure below.) pH 10 11 12 13 Bromphenol Blue Methyl Orange Bromcresol Green Methyl Red Alizarin Bromthymol Blue Phenol Red o-Cresolphthalein Phenolphthalein The pH ranges shown are approximate. Specific transition ranges depend on the indicator solvent chosen. a. bromphenol blue Oyellow green blue O red O colorless b. bromthymol blue Oyellow O green O blue O red O olorless c. bromcresol green Oyellow O green blue Ored O colorless d. o-cresolphthalein

BONUS: During a titration, ammonia is added to the flask and titrated with HCI. Looking at the titration below and the indicator table, what would be a good indicator to use for this experiment? What color change would be observed? 12 10 20 40 60 80 100 120 140 mL d.1 M HCI TABLE 16.7 Common Acid-Base Indicators Approximate pH Range over which the Color Changes Color Change Gower to higher pH) Indicator Thymol blue Micdni otanpr 3234 Filyl d Mechyl purple Broeno purpk

A student obtains the following data from the Determining the pKa of an Acid-Base Indicator experiment. Using this data, calculate the pKa of the indicator in the fourth solution. Solution Abs. pH 3.4 + HCI 0.054 pH 4.6 + NaOH 0.564 Sample # actual pH Abs. 1 3.48 0.130 2345 3.77 0.217 3.99 0.296 4.37 0.388 4.54 0.468 Your Answer: Answer (2 points) After creating a graph of pH versus log([HIn]/[In-]), the following trendline is obtained. = -1.0291× + 3.721 y=-1 Calculate the pKa of bromophenol blue from this data to three decimal places. Your Answer: Answer MacBook Pro

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M of NaOH: 0.100 Volume  of HCI 25mL = 0.025L Moles of HCI = 2.5 mol What is the Volume of  NaOH  equivalence point: What is  Moles of NaOH  equaivalence point: What  is pH at equivalence point? What is calculated pH and experimental pH of NaOH at 0.00 mL , 12.50 mL, 25mL, and 30 mL. Also what is the Error percentage for each one?