Analytical Chemistry – part 1

A 750-mg sample of butter was analyzed by the Kjeldahl method. 50 mL of excess 0.16 M HCl were used and 7.67 mL back titration with 0.0500M NaOH was required to titrate the liberated ammonia. Calculate the percentage of protein in the sample. Use 6.38 for butter.

A sample of impure salicylic acid, C₆H₄(OH)COOH (one titratable proton), is analyzed by titration. What size sample should be taken so that the percent purity is equal to five times the milliliters of 0.0500 M NaOH used to titrate it?

Consider the titration of 40 mL, 0.2 M Acetic acid using 0.4 M NaOH as the titrant.

Solve for the initial pH (Before titration)

Consider the titration of 40 mL, 0.2 M Acetic acid using 0.4 M NaOH as the titrant.

Solve for the pH of the solution, after adding 10 mL of NaOH

Consider the titration of 40 mL, 0.2 M Acetic acid using 0.4 M NaOH as the titrant.

Determine the volume of NaOH required to reach the equivalence point.

Consider the titration of 40 mL, 0.2 M Acetic acid using 0.4 M NaOH as the titrant.

Calculate for the pH at the equivalence point.

The aluminum in a 759.08 mg of impure sulfate sample was precipitated as Al(OH)₃ and ignited at 1100⁰C to yield a precipitate of Al₂O₃ weighing 387.953 mg. Express the result of the analysis in terms of %Al (MW = 27).

A 0.2356 g sample containing only NaCl and BaCl₂ yielded 0.4637 of dried AgCl, upon reaction with excess AgNO₃. Calculate the %NaCl in the sample.

Which of the following salts give acidic aqueous solutions?

(1) KNO₃                    (2) KCH₃COO          (3) NH₄NO₃          (4) RbI
(5) (NH₄)₂SO₄          (6) BaCl₂                     (7) NaCN             (8) KNO₂

A 500-mg sample containing NaOH (40), Na₂CO₃ (106), NaHCO₃ (84), either alone or in compatible combination is treated with 12.95 mL of 0.100 M HCl to reach the phenolphthalein endpoint and an additional of 18.76 mL to reach the methyl red endpoint.

Identify the compounds (aside from the inerts) present in the sample.

A 500-mg sample containing NaOH (40), Na₂CO₃ (106), NaHCO₃ (84), either alone or in compatible combination is treated with 12.95 mL of 0.100 M HCl to reach the phenolphthalein endpoint and an additional of 18.76 mL to reach the methyl red endpoint.

Calculate the % Sodium Carbonate

A 500-mg sample containing NaOH (40), Na₂CO₃ (106), NaHCO₃ (84), either alone or in compatible combination is treated with 12.95 mL of 0.100 M HCl to reach the phenolphthalein endpoint and an additional of 18.76 mL to reach the methyl red endpoint.

Calculate the percentage of inert in the sample.

An iron ore is analyzed for iron content by dissolving in acid and converting all iron species to Fe²⁺. Fe²⁺ ions are then titrated with standard 0.0150 M K₂Cr₂O₇ solution, converting them to Fe³⁺. 35.6 mL is required to titrate the iron in a 1.68-g ore sample. Calculate the % Fe₂O₃
MW (Fe = 55.85, O = 16)

The pH of a household white vinegar solution is 2.45. The vinegar has a density of 1.09 g/mL. What is the mass percentage of acetic acid in the solution?

A 750.25-mg of alloy nickel was dissolved and treated to remove the impurities. The ammoniacal solution was treated with 50 mL of 0.1075 M KCN and the excess cyanide required 2.25 mL of 0.00925 M AgNO₃. Determine the %Ni (58.7) in the alloy.

The TI in a 9.76-g sample of rodenticide was oxidized to the trivalent state and treated with an unmeasured excess Mg/EDTA solution. The reaction is

Tl³⁺ + MgY^2- → TlY^– + Mg²⁺

Titration of the liberated Mg²⁺ required 13.34 mL of 0.03560 M EDTA. Calculate the percentage of Tl₂SO₄ (504.8 g/mol) in the sample.

Determine the number of grams of C₂H₅N that will heat with 81.81g of oxygen in the equation: C₂H₅N + O2 → CO + H₂O + NO

Determine the number of moles of an unknown base in a solution when titrated with 0.15M HCl and 22.01mL of the acid were needed to reach the end point of the titration.

What is the Nujol Mull in organic chemical reactions?

Define a salt in terms of acid and base.