Exam 28: Gravimetric and Combustion Analysis

The iron content of an iron supplement must be determined.The manufacturer states that each tablet contains 1 000.0 mg of bioavailable iron.A tablet with a mass of 4.9283 grams is digested in nitric acid to release Fe³⁺ into solution.After filtration,the iron in solution will be precipitate with sodium bicarbonate.What is the minimum mass sodium bicarbonate must be added to precipitate the iron in solution? Assume no sources of interfering metals are present.

A 100.00 mL solution of copper(II)chloride is reacted with excess silver nitrate to precipitate 8.9260 g silver chloride.Which of the calculations below is NOT required to calculate the molarity of the copper(II)solution?

Homogeneous precipitation occurs when a precipitant is generated slowly from within an initially homogeneous solution by a chemical reaction.The main benefit from homogeneous precipitation is:

Silver cation is precipitated from solution using sodium carbonate.Calculate the gravimetric factor to relate the mass of the product to the analyte.

Which of the following are techniques to promote particle growth? I Use a large volume of solution so concentration of analyte and precipitant are low. II Rapidly add the precipitant to precipitate all analyte from solution,then raise the temperature of the solution to promote crystal growth. III Slowly adding precipitant with vigorous mixing as the precipitant is added to prevent a highly supersaturated condition in solution. IV Raise the temperature of the solution to increase solubility of precipitate and decrease supersaturation.

A solution is prepared from an unknown solid containing Ni and Cu by dissolving 5.2832 grams of the solid in nitric acid to release Ni²⁺ and Cu²⁺.The nitric acid is neutralized and the solution diluted to 200.0 mL.Next excess sodium carbonate is added to the solution to form Ni and Cu carbonates with a total mass of 2.5305 grams.The precipitate is then ignited to form NiO and CuO with a total mass of 1.6126 grams.What is the percent by mass Ni and Cu in the solid sample?

Modern combustion analysis uses gas chromatography to measure the amounts of product gas released.Which detector is used with the GC?

The final precipitation product should have a known,stable chemical composition.One way to obtain a known,stable chemical composition is via____________________ ,which is defined as the strong heating of a precipitate to change the chemical composition of the precipitate to a more stable form.

Which of the following statements is(are)true for precipitate particle size? I Particle size must be large enough to not clog or pass through a filter. II Particle size is controlled by precipitation conditions. III Thermodynamics favors larger crystals because the surface atoms have higher energy than internal atoms and the fraction of atoms on the surface is smaller for larger crystals than smaller crystals. IV Ostwald ripening is the process where smaller particles re-dissolve and larger crystals grow.

Combustion analysis of 0.1938 grams of a hydrocarbon increased the mass of the water trap by 0.2750 grams and the mass of the carbon dioxide trap by 0.5973 grams.What is the empirical formula for the hydrocarbon?

____________________ are solid particles that lack any crystalline order.

Crystallization occurs when precipitant is added to a solution,creating a temporary supersaturated solution.Crystallization occurs in two stages: nucleation and particle growth.Which of the following is NOT true for nucleation and particle growth? I Nucleation occurs when solutes form clusters of sufficient size which reorganize into a more ordered structure capable of growing into larger particles. II Particle growth occurs when ions,molecules,or other nuclei condense onto a particle to form a larger crystal. III Sources of nucleation are solution impurities or small scratches on a glass surface. IV Particle growth occurs when amorphous particles clump together to create larger amorphous particles.

Combustion analysis of C,H,and S converts each element into nonmetal oxide for analysis.Combustion analysis of O requires a different approach.Which of the steps below is(are)not required or false for combustion analysis for O? I Sample is thermally heated to decompose the compound in the absence of O₂. II Gaseous products from pyrolysis are passed through nickelized carbon at 1 075 ^oC to convert oxygen into CO. III Gaseous products are sent to GC for analysis. IV Halogens are converted to HX during pyrolysis,dissolved in water and titrated with silver nitrate. V Gaseous products from pyrolysis are passed through nickelized carbon at 1 075 ^oC to convert oxygen to CO₂.

Precipitates will often contain impurities and will require treatment to remove impurities.Which of the following precipitation terms is INCORRECTLY defined?

A 100.0 mL sample of a solution containing copper(II)cation is treated with excess sodium carbonate to precipitate 3.6055 grams of copper(II)carbonate.What is the molarity of the solution?

Which of the following is NOT true for traditional combustion analysis of a hydrocarbon?

Modern combustion analysis uses dynamic flash combustion.What is the main reason dynamic flash combustion is employed?

Which of the properties below is NOT a property of the ideal solid product for gravimetric analysis?

____________________ are solid particles with long-range order.

Combustion analysis of 0.1938 grams of a hydrocarbon increased the mass of the water trap by 0.2750 grams and the mass of the carbon dioxide trap by 0.5973 grams.What is the percent by mass for C and H?