A chemist received different mixtures for analysis with the statement that they contained NaOH, NaHCO3, Na2CO3 or compatible mixtures of these substances together with inert material. From the data given, identify the respective materials. Sample 4. The sample was titrated with acid until the pink of phenolphthalein disappeared; this process required 39.96 mL. On adding an excess of the acid, boiling and titrating back with NaOH, it was found that the base was equivalent to the excess acid. A. NazCO3, NaHCO3 В. NaHCOз O C. Na2CO3 O D. None of these OE. NAOH

A chemist received different mixtures for analysis with the statement that they contained NaOH, NaHCO3, Na2CO3 or compatible mixtures of these substances together with inert material. From the data given, identify the respective materials. Sample 4. The sample was titrated with acid until the pink of phenolphthalein disappeared; this process required 39.96 mL. On adding an excess of the acid, boiling and titrating back with NaOH, it was found that the base was equivalent to the excess acid. A. NazCO3, NaHCO3 В. NaHCOз O C. Na2CO3 O D. None of these OE. NAOH

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter21: Potentiometry

Section: Chapter Questions

Problem 21.22QAP

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A sample may contain NaOH, NazCO3 and NaHCO3, alone or in some combination, along with inert material. A samplewitha mass of 857.6 mgwas dissolved and titrated with0.1163 M HCI. The volume of HCl used from 0 to methyl red endpoint (Phenolphthalein endpoint was not monitored here) was found to be 36.54 mL. Another 228.8 mg portion of the sample was titrated to the phenolphthalein endpoint and 10.82 mL was used up for this titration. a. What is the composition of the sample? b. Calculate the percentage of each of the component present.
You are asked to determine the alkali present and the percentage of each in a component of a sample material containing components of NaOH, Na,co, and NaHCo, or mixtures of this together with inert material. Each sample being tested weighs 29 and uses hydrochioric acid for neutralization. Sample 1: Using phenolphthatein indicator. 48.64ml acid was used. A dupilcate sample needed 97.28mi of acid was used with methyl orange indicator. Sample 2: No color change using phenolphthalein as an indicator but with methyl orange 76.94mi acld is required. Sample 3. To cause a color change., the sample was titrated cold with phenolphthalein, 30.58ml of acid is necessary.and an addifional 33.19ml was required for complete neutralization Sample 4: The process required 79.92ml of acid until the pink of phenolphthalein disappeared. On adding the excess of the acid, boling and titrating back with alkali, it was found that the alkall was exactly equivalent to the excess acid added,
2.413 g sample contains Na2CO3, NaHCO3 and inert material. This sample was solved in water and diluted to 250.0 ml. 80 ml solution was taken and titrated with 0.09644 N HCl with the indicator of phenolftalein. 6.13 ml HCl was consumed. From a second solution, again 80 ml was taken and titrated with the same HCl solution with the indicator of methylorange. 15.4 ml HCl was consumed. Calculate the percentage of NaHCO3 and Na CO in sample (Na CO =106.0 g/mol, NaHCO =84.02 g/mol)
Na2CO3 served as the primary standard in a titration experiment. Find the molarity of the titrant given the following data in 3 decimal places. Show solutions Primary Standard Used: Na2CO3Formula Mass of 1º standard: 105.99 g/mol% purity of 1º standard: 95% Trial 1 2 3 1º Standard weight, g 0.1005 0.1001 0.0997 Net volume of HCl, mL 9.30 9.00 8.90 Molarity of HCl X1 X2 X3
A sample is known to contain about 20% soda ash. What sample size should be taken for analysis, if it is to be dissolved into a 50 mL volumetric flask, with 10 mL aliquots analyzed, if it is desired that the analysis consume a total of 40 mL 0.10 M HCl with 10 mL of 0.10 M NaOH used in the back-titration, after boiling.
A 2.345 g sample of an oat cereal is determined by a Kjeldahl analysis. The sample is digested with H₂SO4, the resulting solution made basic with 45% NaOH, and the NH3 distilled into 50.00 mL of 0.1150 M HCI. The excess HCI is back titrated using 29.30 mL of 0.140 M NaOH using mixed indicator (bromocresol green and methyl red). 1. If the protein in grains averages 15.50% w/w N, what is the % w/w protein in the sample? 2. Why is a mixed indicator used in nitrogen analysis? (Answer in 200 words or less.)
3) In the treatment of myasthenia gravis, 10 mg of guanidine (NH-C(NH2)2) per kilogram of body weight is given. Nitrogen in a sample with a total mass of 7.50 g and containing 4 tablets is converted to ammonia by Kjeldahl decomposition. It is then distilled into 100 mL of 0.1750 M HCI. Performed analysis; titration of excess acid with 11.37 mL of 0.180 M NaOH solution. Accordingly, in which option is the number of tablets at the appropriate dose given for a 48 kg patient? (C-12.0 g/mol; H=1 g/mol; N = 14.0 g/mol; Cl=35,5 g/mol) a) 3 b) 6 c) 9 d) 12 f) 15
Calculate the percentage CH3COOH in a sample of vinegar from the following data.Sample = 15.00 g, NaOH used = 43.00 ml ; 0.600 N H2SO4 used for back titration =0.250 ml ; 1.00ml NaOH is equivalent to 0.0315 g H2C2O4. 2H2O.
5. A 300.0 mg sample containing Na,CO3, NaHCO, and NaOH and inert material either alone or in some combination was dissolved and titrated with 0.1000 M HCI the titration required 24.41 ml to reach the phenolphthalein endpoint. And an additional 8.67 mL to reach the methyl red endpoint. Determine the composition of the sample and calculate the percent of each titrated component.
From the following data find the percentages of Na2CO3 and NaHCO3 in a mixture of these chemicals and inert constituents: a) A 0.5000 g sample required 45.50 mL 0.1050 N HCl to reach the methyl orange end point. b) 25.00 mL of 0.1000 N KOH is added to 0.2500 g of the sample; BaCl2 is added to precipitate the BaCO3 and 12.00 mL 0.1050 N HCl is required to reach the phenolphthalein end point.
The graphic below shows the general procedure for titrating the saturated solution of magnesium hydroxide with hydrochloric acid. Select all of the true statements from the choices below. 1. Obtain a saturated solution of magnesium hydroxide. 0 2. Transfer 30.0 mL to an Erlenmeyer flask using a volumetric pipet. Add phenolphthalein. 3. Titrate to a colorless endpoint using 0.0020 M hydrochloric acid. It is important that the aliquot drawn in step 2 does not contain undissolved magnesium hydroxide solid. For titrations of the saturated solutions at elevated temperatures, the solution must be held at high temperature for the duration of the titration. Hydrochloric acid is the analyte in this titration. The volume of liquid in the buret should be read before and after the titration. At the endpoint of the titration, the solution will turn from colorless to pink.
Benzoic acid extracted from 123.16 g of sample required a 27.13 mL titration with 0.0792 M barium hydroxide. What is the percent benzoic acid in the sample?