Organic Chemistry Answers

A sample of meat scrap weighing 2.000 g is digested with concentrated sulfuric acid and a catalyst. The resulting solution is made alkaline with NaOH and the liberated ammonia distilled into 50.00 mL of 0.6700 N HCl. The excess acid then requires 30.10 mL of 0.6520 N NaOH for neutralization. What is the percentage of the protein in the meat? The Kjeldahl factor is 6.25.

A 0.7500-g carbonate mixture was dissolved in water and then titrated with 0.2000 N HCl, requiring 24.20 mL for the phenolphthalein endpoint. In another flask, 40.20 mL of the acid was required to reach the bromocresol green endpoint. Calculate the %NaOH, %NaHCO₃, and %Na₂CO₃ in the mixture.

A 0.3606-g of a weak monoprotic was dissolved in water and then titrated with 0.1040 N KOH solution. A total of 28.39 mL of the base was consumed in the titration to reach the endpoint. What is the equivalent weight of the acid? If the pH at ½ EP is 4.194, what is the Ka of the acid?

Calculate the amounts of solids Na₂HPO₄ and NaH₂PO₄ needed to prepare 0.40 M, 1.5L of phosphate buffer with pH of 7.0.

Calculation the pH of the following systematically. Make sure to include the pertinent reactions and equations.

a. 2.5 x 10 ^-7 M HNO₃

b. 2.0M CH₃NH₂ (K_b = 5.0 x 10 ^-4)

c. 0.45M HNO₂ (K_a = 4.0 x 10 ^-4)

Write the MBE, PBE and CBE for the following:

a. 0.15M H2CrO4

b. 0.35M KClO4

c. 0.50M NaHSO4

A mixture that contains AgCl and AgBr only was analyzed and found to contain 66.32% Ag. What is the percentage of Br in the mixture?

A feldspar sample was analyzed. In the analysis of 0.4270-g sample, a mixture of KCl and NaCl is obtained weighing 0.0716 g. The KCl is then converted to 0.1558 g of K2PtCl6 by chemical reaction. Calculate the percentage of Na2O in the feldspar.

The N in a 0.4984-g sample of organic material is converted to NH4HSO4 by digestion with concentrated H2SO4. If the NH4+ ions are precipitated as (NH4)2PtCl6 and the precipitate is ignited to Pt, what is the percentage of N in the sample if the Pt weighs 0.1876 g?

An impure magnetite (Fe3O4) sample weighs 0.5023 g. This is converted to Fe2O3 by chemical reactions. The Fe2O3 obtained weighs 0.3995 g. What is the percentage of Fe3O4 in the magnetite?