Answer to Question #140303 in General Chemistry for Sohyun Ravena

Question

Fe(OH)3sol? How is it formed? What is/are expected characteristic/s of the Fe(OH)3sol? Is it lyophilic or lyophibic system?
2. What kind of colloidal system is the calxium acetate gel? How is it formed? What is/are expected characteristic/s of the calcium acetate gel?
3. What kind of colloidal system is the benzene/detergent mixture? Howis it formed? What is/are expected emulsion? What is the role of detergent in the preparation of this emulsion? Is the emulsion the same emulsion? Why? Why not?
4. How you described the smoke that was formed from the cigarette? What kind of colloidal system does the cigarette smoke belongs? What is/are expected characteristics of colloidal system?

Answer 1

1. Ferric hydroxide forms a hydrophobic sol. Hence it is prepared indirectly by the hydrolysis of ferric chloride with boiling water. The reaction takes place as follows:FeCl3​+3H2​O→Fe(OH)3​+3HCl

2. Calcium acetate is a chemical compound which is a calcium salt of acetic acid. It has the formula Ca(C₂H₃O₂)₂. Its standard name is calcium acetate, while calcium ethanoate is the systematic name. An older name is acetate of lime. The anhydrous form is very hygroscopic; therefore the monohydrate (Ca(CH₃COO)₂•H₂O) is the common form.

3.It is a heterogeneous system consisting of two phases (i) Dispersed phase and (ii) Dispersion medium. If the dispersion medium is water, the colloidal solutions are called hydrosols or simply sols. If alcohol or benzene is the dispersion medium, it is called alcosol or benzosol etc.

Emulsion can be stabilized by increasing the repulsion between the dispersed phase i.e., by increasing the electrostatic repulsion (which is long range) or steric repulsion (short range). Emulsifiers are amphiphiles that reduce the interfacial tension between the two phases and contribute to the stabilization of dispersed droplets with electrostatic or steric effects.

4. Colloidal Solution is a heterogeneous mixture in which particle size of substance is intermediate of true solution and suspension i.e. between 1−1000 nm. Smoke from a fire is example of colloidal system in which tiny particles of solid float in air. Just like true solutions, colloidal particles are small enough and cannot be seen through naked eye. They easily pass through filter paper but colloidal particles are big enough to be blocked by parchment paper or animal membrane.Hence, smoke is a colloidal system of carbon dispersed in air.