A aqueous solution of the monoprotic weak acid HX is prepared at

CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases

Problem

0.250\,\text{M}

aqueous solution of the monoprotic weak acid HX is prepared at

25\,^{\circ}\text{C}

. At equilibrium the acid is found to be

3.2\%

ionized. (a) Calculate the equilibrium hydronium-ion concentration

[\text{H}_{3}\text{O}^+]

in the solution. (b) Determine the numerical value of the acid-dissociation constant

K_a

for HX at

25\,^{\circ}\text{C}

. (c) Compute

pK_a

for HX and compare its value to that of acetic acid (

pK_a = 4.76

). Indicate which acid is stronger and justify your answer briefly.