Question

multiple choice assuming that all of the following substances are permeable across a selectively permeable membrane, which of the following molecules would you predict to move fastest across the membrane? sucrose (mw = 342 g/mol) glucose (mw = 180 g/mol) citric acid (mw = 192 g/mol) iodine (mw = 127 g/mol) hydrochloric acid (mw = 36 g/mol)

Explanation:

To determine which molecule moves fastest across a selectively permeable membrane, we consider molecular weight (MW). Smaller MW means smaller molecule size (usually), and smaller molecules diffuse faster (assuming similar solubility/charge). Let's list the MWs:

• Sucrose: 342 g/mol
• Glucose: 180 g/mol
• Citric acid: 192 g/mol
• Iodine: 127 g/mol
• Hydrochloric acid (HCl): 36 g/mol

HCl has the lowest MW (36 g/mol), so it is the smallest molecule here and should diffuse fastest.

Answer:

hydrochloric acid (mw = 36 g/mol)