question_answer 1)

  Why does hard water not form lather with soap?

Answer:

  Soap is sodium or potassium salt of higher fatty acids. When hard water containing \[C{{a}^{2+}}\] and \[M{{g}^{2+}}\] ions is treated with soap solution, the fatty acids anions combine with \[C{{a}^{2+}}\] and\[M{{g}^{2+}}\] ions and form curdy white precipitates. As a result hard water does not produce lather with soap. \[\underset{Soap}{\mathop{2{{C}_{17}}{{H}_{35}}COONa}}\,+CaC{{l}_{2}}\to \underset{Curdy\,white\,ppt.}{\mathop{{{({{C}_{17}}{{H}_{35}}COO)}_{2}}Ca\downarrow +2NaCl}}\,\]