On which of the following is the solubility of a gaseous substance dependent?  I. Nature of solvent  II. Nature of solute  III. Temperature  IV. Pressure

Step 1: Analyze the question You are asked which factors affect how much of a gas dissolves in a liquid. You have to check each of the four factors.

Step 2: Explain the concept The solubility of a gas depends on several things:

• I. Nature of solvent: Yes. A gas dissolves differently in different solvents. For example, ammonia is very soluble in water (a polar solvent) but much less so in a non-polar solvent. "Like dissolves like" applies here.
• II. Nature of solute: Yes. Different gases have different solubilities in the same solvent. HCl and NH₃ are highly soluble in water, while O₂ and N₂ are only slightly soluble.
• III. Temperature: Yes. Gas solubility usually decreases as temperature rises. This is why warm soda goes flat faster than cold soda.
• IV. Pressure: Yes. By Henry's Law, the solubility of a gas is directly proportional to its partial pressure above the liquid:

S = kP

This is why a fizzy drink bubbles when you open the bottle and the pressure drops.

Step 3: Solution All four factors (I, II, III and IV) affect the solubility of a gas.

• Option B (I and II only) leaves out temperature and pressure.
• Option C (II only) leaves out three factors.
• Option D (III and IV only) leaves out the nature of the solvent and solute.

Step 4: Answer The correct option is A. I, II, III and IV.

Tip: Remember the four factors as "S-S-T-P": Solvent, Solute, Temperature, Pressure. If a JAMB question asks about gas solubility and lists all four, "all of the above" is usually the right choice. Also remember that for gases, higher temperature means lower solubility, and higher pressure means higher solubility.