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po ". IN 11 AaBb AaBb АавbccDd AaBbccDd AaBbc АаВЫСcl HaD АавьСcD > 트 1 Normal I No Spac... Heading 1 Heading 2 Title Subtitle 三三三三三、 A > zi Paragraph Styles Question 1. (Quantitative Analysis) [20 marks] a. 25 mL of 0.1 M lactic acid (HC3H5O3, pka= 3.86) was transferred o a conical flask and titrated with 0.15 M NaOH solution i. Calculate the pH of the solution after adding 0 mL of NaOH. Show all workings. (6 marks) ii. Indicate how many mL of 0.15 M NaOH must be added to the lactic acid solution to reach the equivalence. Show all workings. (2 marks) iii. From the list below, select the appropriate indicator for this titration. Explain your answer (2 marks) Indicator Acid Color Base Color pH range pka Methyl orange red orange 3.1-4.4 3.7 Yellow purple 5.2-6.8 6.1 Bromocresol purple yellow blue 6.0-7.6 Bromothymol blue 7.1 phenolphthalein colorless red 8.3-10.0 8.9 I b. Quantitative determination of the ibuprofen content of a tablet gave the following results: Measurement 1: 300 mg Measurement 2: 295 mg Measurement 3: 301 mg Measurement 4: 305 mg Measurement 5: 299 mg i. Calculate the mean value of ibuprofen (in moles) present in the tablet. The molecular mass of ibuprofen is 206.28 g/mol. [2 marks] Calculate the standard deviation and the confidence interval for the true value at 95% confidence interval. [4 marks] ii. } N B ))) W