Question

Chloride which is insoluble in water is:
A.Sodium chloride
B.Potassium chloride
C.Mercurous chloride
D.Calcium chloride

Answer 1

Hint:
Chlorine is a halogen. It has a high value of electronegativity and forms anion $(C{l^ - })$ as chlorine atoms accept one electron to attain the nearest noble gas configuration. Chlorine being electronegative forms compounds with electropositive metals. Ionic compounds have the highest solubility in water.

Complete step by step answer:
Chlorine is a non-metal. It forms compounds with metal such as sodium, potassium, calcium, magnesium and so on. These are called chloride salts or more commonly halides.
Sodium chloride has the formula $NaCl$ . It is an ionic compound and is known as common salt. Ionic bond is present between $N{a^ + }$ and $C{l^ - }$ ions. $NaCl$ is soluble in water because water pulls apart the sodium and chloride ions and breaks the ionic bonds between them. Sodium chloride is a polar molecule.
Potassium chloride has the formula $KCl$ . it is also an ionic compound and polar due to the electronegative difference between the potassium and chlorine. ${K^ + }$ and $C{l^ - }$ ions dissolve in water and remain separate and hence is highly soluble in water.
Mercurous chloride has the formula $H{g_2}C{l_2}$ . In this compound the oxidation state of mercury is $ + 1$ . It is also known as calomel and is used in reference electrodes in electrochemistry. It is insoluble in water.
Calcium chloride is also an ionic compound which has the formula $CaC{l_2}$ . It is also highly soluble in water. The bonds between the molecules are broken thus getting soluble in water.
So the chloride insoluble in water is mercurous chloride. The correct option is C.

Note:The chlorides of all metals except the chloride of lead, silver and mercury $(I)$ are soluble in water. Mercurous chloride and silver chloride are insoluble in water.
There are two stable oxidation states of mercury $(H{g^ + },H{g^{2 + }})$ . Compounds having $H{g^{2 + }}$ are mercuric compounds.