11 - GRAVIMETRIC ANALYSIS

A. 88.21

1. If a 0.3800 g sample of sodium sulfate yielded 0.55 g of barium sulfate precipitate by gravimetric assay, what would be the percentage purity of sodium sulfate? At.wt.: Ba = 137.3; S = 32.06; Na = 23; O = 16

   A. 88.21

   B. 99.94

   C. 99.15

   D. 88.51

D. 113.7%

2. If a 0.47 g sample of potassium iodide yielded 0.7564 g of silver iodide precipitate by gravimetric assay, compute for the % purity of the potassium iodide. MW KI = 165.90; MW AgI = 234.76

   A. 83.7%

   B. 93.7%

   C. 103.7%

   D. 113.7%

B. Physical

3. In gravimetric analysis, when the process used in extraction to obtain the original constituent, this method belongs to:

   A. Chemical

   B. Physical

   C. Precipitation

   D. Any of the above

A. 0.70668

4. Solve for the gravimetric factor, if a 0.235 g sample of potassium iodide yielded 0.3782 g of silver iodide precipitate by gravimetric assay, compute for the % purity of the potassium iodide.

   A. 0.70668

   B. 1.41507

   C. 0.62136

   D. 1.60936

B. Gravimetric

5. Analysis wherein the constituents of a sample are separated and then the product is weighed:

   A. Volumetric

   B. Gravimetric

   C. Special method

   D. Gasometric

C. Gravimetry

6. Assay of NaCl in table salt by precipitation as AgCl, filtration, drying and weighing the residue is classified as

   A. Direct precipitimetry

   B. Volhard’s method

   C. Gravimetry

   D. Residual precipitimetry

• Law of Mass Action

• Reversible Reactions

• Solubility Product principle

• Common Ion Effect

The chemical reactions in gravimetric analysis take place in accordance with the established laws and theories of chemistry:

Gravimetric Methods

• The measurement of the weight of a substance in a sample

• Calculation of the weight of a substance in a sample from the weight of a chemically equivalent amount of some other substance

Physical Methods

• the substance to be measured gravimetrically is separated from other substances composing the sample

• by physical methods, purify and weigh without chemical change

• Frequently used in pharmaceutical analysis

Chemical Methods

• Employed when other components of the sample are such that separation by physical means of the substance being measured is not possible or convenient

• Convert the substance to a chemically equivalent amount of some other substance which can be separated, purified and weighed

Gravimetric Factor

the MW weight of the sample proportionate to the MW weight of residue/precipitate obtained from it

Chemical Factor

Gravimetric Factor is also known as

Gravimetric Factor formula

other Gravimetric Factor formula: