Concept:Strong acids ionize completely in water while weak acids ionize partially, so methods that measure ion concentration can distinguish them.
Explanation:A strong acid releases many
H+ ions in solution, giving high electrical conductivity and a low pH value.
A weak acid releases fewer
H+ ions, so it shows lower conductivity and a higher pH value.
Measurement of heat of reaction also works because strong acids have a higher enthalpy of neutralization than weak acids.
However, litmus paper only indicates whether a solution is acidic or basic, not how strong the acid is.
All acids turn blue litmus red, whether they are strong or weak.
Therefore, litmus paper cannot be used to distinguish between strong and weak acids.
Answer:B. The use of litmus paper