Which fatty acid salt is soluble in water solutions? a) rcoo-k+ b) (rcoo-)2mg2+ c) (rcoo-)2ca2+ d) none are soluble

Answer is (A)
Pottasium and Sodium salts are soluble in water. When these soaps are added to hard water. Hard water contains calcium or magnesium ions and they form Magnesium or Calcuim salts. These salts of magnesium and calcium precipitates out and are insoluble in water. This precipitation is called as dirt (the exact word for dirt is not acceptable here). This process is considered as the disadvantage of soap as well as using hard water.

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer