Surface Chemistry - Practice Questions with Answers
75 free MCQs on Surface Chemistry, each with its own worked answer and explanation. 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.
75 practice questions on Surface Chemistry, sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Surface Chemistry notes.
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.
Easy - 25 questions
Q1.
The uniform distribution of a substance throughout the bulk of a solid or liquid is called:
A negatively charged colloidal sol is coagulated by adding electrolytes containing Na+, Ba<sup>2+</sup>, and Al<sup>3+</sup> ions separately. According to the Hardy-Schulze rule, which ion will coagulate the sol most effectively?
Why is a multimolecular colloid like a gold sol different from a macromolecular colloid like a protein solution?
A A multimolecular colloid is itself largely made up of a single enormous giant covalent molecule with little aggregation needed in most cases under typical conditions
B A multimolecular colloid is formed by aggregation of many small atoms or molecules, while a macromolecular colloid consists of single large polymer molecules
C Macromolecular colloids such as dissolved proteins are said to be inherently unstable whenever placed in aqueous solution according to standard textbooks
D Multimolecular colloids are said to invariably carry a permanently fixed negative surface charge in every case in general practice as frequently described
A given mass of activated charcoal adsorbs a gas according to the Freundlich isotherm with n = 2. If the pressure of the gas is quadrupled, by what factor does x/m increase, all else being constant?
A colloidal sol of As<sub>2</sub>S<sub>3</sub> is negatively charged. Which combination correctly ranks the coagulating power of NaCl, MgCl<sub>2</sub>, and AlCl<sub>3</sub> from least to most effective, based on the Hardy-Schulze rule?
A AlCl<sub>3</sub> less than MgCl<sub>2</sub> less than NaCl
B NaCl less than MgCl<sub>2</sub> less than AlCl<sub>3</sub>
C MgCl<sub>2</sub> less than NaCl less than AlCl<sub>3</sub>
D All three are equally effective regardless of cation charge
Why can a catalyst not alter the position of equilibrium of a reversible reaction, even though it increases reaction rate?
A A catalyst is said to selectively affect mainly the reverse reaction pathway, leaving the forward reaction rate largely untouched and unchanged under most conditions encountered
B A catalyst lowers the activation energy of both forward and reverse reactions equally, so both rates increase proportionally and equilibrium is reached faster but at the same position
C A catalyst is said to directly alter the fundamental numerical value of the reaction's equilibrium constant itself as frequently observed in practice in many documented cases according to conventional understanding
D A catalyst is said to function effectively mainly on exothermic reactions and to have no useful effect on endothermic ones in routine practice overall in most cases under typical conditions
Gold sol prepared by reduction of gold salts is stabilized by adsorbed negative ions on its surface. If a small amount of a strongly hydrated lyophilic colloid such as gelatin is added before adding an electrolyte, the gold sol becomes more resistant to coagulation. This protective effect is best explained by:
A Gelatin is said to completely and permanently neutralize the entire surface charge carried by every gold particle present
B Gelatin forms a protective hydrophilic coating around the lyophobic gold particles, reducing their tendency to aggregate
C Gelatin is said to chemically react directly with the gold atoms themselves to form a brand new compound
D Gelatin is said to noticeably raise the temperature of the surrounding sol, and this is what prevents coagulation
Which statement correctly distinguishes a gel from a sol and an emulsion?
A A gel is instead described as a liquid dispersed throughout a continuous surrounding gas phase, while a true sol is a fine solid dispersed evenly throughout that same gas phase
B A gel has a liquid dispersed in a solid medium forming a semi-solid network, while a sol is a solid dispersed in a liquid, and an emulsion is liquid dispersed in liquid
C A gel and an emulsion are in fact said to be largely identical to one another in their overall phase composition and structure under most conditions encountered
D A gel is instead described as mainly containing a gaseous substance as its single dispersed phase, as frequently observed in practice in many documented cases
In delta formation at a river mouth, fine clay and silt particles carried by river water as a negatively charged colloidal sol settle out. What is the most likely chemical reason for this?
A River water cools suddenly upon meeting the sea, physically freezing the suspended particles according to standard textbooks
B Sea water contains a high concentration of electrolytes whose cations coagulate the negatively charged clay sol
C Sunlight at the river mouth chemically breaks down the colloidal clay particles in general practice as frequently described
D River water evaporates unusually rapidly right at the point it meets the sea in most textbook accounts during normal conditions
Why does increasing pressure favor physisorption more strongly at lower temperatures than at higher temperatures?
A Pressure is said to have little genuine measurable effect on adsorption at any given fixed temperature, in general practice as frequently described in most textbook accounts
B At lower temperatures, gas molecules have less kinetic energy to escape the weak attractive forces holding them to the surface, so increased pressure packs more molecules onto the surface effectively
C Higher ambient temperature is said to usually increase the overall degree of physisorption regardless of whatever pressure happens to be applied, during normal conditions as generally observed
D Physisorption is said to be largely independent of both the surrounding gas pressure and the ambient temperature in most cases, in typical laboratory settings under usual circumstances
A protective colloid is added to a lyophobic sol before adding an electrolyte to prevent coagulation. The effectiveness of a protective colloid is expressed using gold number. What does a lower gold number indicate about a protective colloid?
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
Why does a finely divided catalyst, such as platinum black or Raney nickel, generally show higher catalytic activity than the same mass of catalyst in a bulk lump form?
A Finely divided catalysts undergo a change in chemical composition compared with the bulk form
B Finely divided catalysts react chemically with the reactants rather than acting catalytically
C Greater subdivision increases the total surface area available for adsorption of reactant molecules
D Bulk catalysts generally have a higher melting point, which tends to slow down the reaction