Question

Which one of the following forms a negativity charged sol?

• A. $A{l}_2{O}_3.x{H}_{2}O$
• B. $C{r}_2{O}_3.x{H}_{2}O$
• C. $Ti{O}_2$
• D. $CdS$

Answer 1

Answer: (D)

$CdS$

CdS is the negatively charged sol. Depending upon the nature of charge on the particles of the dispersed phase, the colloidal solutions are classified into positively charged and negatively charged colloids. Some typical examples are as follows:

(a) Negatively charged colloids (b) Positively charged colloids

• Metal sulphides: As₂S₃, CdS • Metal hydroxides: Al(OH)₃, Fe(OH)₃

• Metal dispersions: Ag, Au, Pt • Metal oxide: TiO₂

• Sulphur sol • Basic dyes: Methylene blue

• Sols of starch, gums, gold, gelatin etc. • Haemoglobin