Answer: It has greater protective power, since a smaller amount is needed to prevent coagulation of the gold sol.
- A It carries a stronger positive charge that tends to repel the electrolyte ions under most conditions studied
- B It adsorbs poorly onto the surface of the gold particles compared with other colloids in most observed cases
- C It has lower protective power, since more of it is needed to stabilise the gold sol under typical physiological conditions
- D It has greater protective power, since a smaller amount is needed to prevent coagulation of the gold sol
Correct answer: D. It has greater protective power, since a smaller amount is needed to prevent coagulation of the gold sol
Explanation: Gold number is the minimum mass in milligrams of a protective colloid needed to prevent coagulation of a standard gold sol on adding electrolyte; a smaller gold number means greater protective power.
A typical adsorption isotherm: x/m (mass adsorbed per gram of adsorbent) rises steeply at low pressure, then flattens into a saturation plateau as the adsorbent surface fills up.
Concept context
Explore the chemistry that happens at interfaces, from catalysts that speed up industrial reactions to colloids like milk, smoke, and gels that surround us every day.