Answer:
Metal ions in water can react with soap to form salts. ( option C)
Step-by-step explanation:
Soaps have the general formula (RCO2−)nMn+ (Where R is an alkyl, M is a metal and n is the charge of the cation).
C17H35COO- Na+
The class of soaps is determined by the identity of Mn+. Those can be mettalic or lithium soaps.
Let's consider those metals are calcium or magnesium ions, dissolved, with soap, in the water, we'll find that the sodium ion (Na+) at the polar end of the soap molecule is replaced by a metal ion such as calcium or magnesium ion. This will result in a salt, ( better said an insoluble fatty acid) salt.
This can be shown with the following reaction:
2 C17H35COO- Na+ + Ca2+ → (C17H35COO)2Ca + 2Na+
This results in Calcium stearate, which is the calciumcarboxylate (calcium salt) of stearic acid.
Metal ions in water can react with soap to form salts.