Question

Temporary hardness of water is due to the presence of the sulphates of Ca and Mg. If this is true enter 1, if false enter 0.

Answer 1

Carbonates and bicarbonates salt decomposes on heating and forms insoluble substances which can be precipitated out. So, temporary hardness can be removed by boiling or lime softening.

Complete answer:
A soft water is the one which forms or produces sufficient lather with the soap. On the other hand, hard water is the one which forms an insoluble scum before it forms lather with the soap. The hardness of natural water is generally caused by the presence of substances like bicarbonates, chlorides and sulphates of calcium and magnesium but infect soluble salts that form a scum with soap causing hardness. The presence of such ions in the soap can be represented as:
${\text{Ca}}_{\left( {{\text{aq}}} \right)}^{ + 2} + 2{{\text{C}}_{17}}{{\text{H}}_{35}}{\text{COO}}_{\left( {{\text{aq}}} \right)}^ - \to {\left( {{{\text{C}}_{17}}{{\text{H}}_{35}}{\text{COO}}} \right)_2}{\text{Ca}}$ and ${\text{Mg}}_{\left( {{\text{aq}}} \right)}^{ + 2} + 2{{\text{C}}_{17}}{{\text{H}}_{35}}{\text{COO}}_{\left( {{\text{aq}}} \right)}^ - \to {\left( {{{\text{C}}_{17}}{{\text{H}}_{35}}{\text{COO}}} \right)_2}{\text{Mg}}$ .
Hardness of water is of two types namely temporary hardness and permanent hardness. Temporary hardness of water can be removed simply by boiling as it is due to the presence of bicarbonate salt of magnesium and calcium ions and the bicarbonates decompose readily and the insoluble carbonates are precipitated. It can be represented as:
${\text{Ca}}{\left( {{\text{HC}}{{\text{O}}_3}} \right)_2}\xrightarrow{{{\text{boiling}}}}{\text{CaC}}{{\text{O}}_{3\left( {\text{s}} \right)}} + {{\text{H}}_2}{\text{O}} + {\text{C}}{{\text{O}}_2}$ and
${\text{Mg}}{\left( {{\text{HC}}{{\text{O}}_3}} \right)_2}\xrightarrow{{{\text{boiling}}}}{\text{MgC}}{{\text{O}}_{3\left( {\text{s}} \right)}} + {{\text{H}}_2}{\text{O}} + {\text{C}}{{\text{O}}_2}$ .
Temporary hardness can also be removed by Clark’s method. On the other hand, permanent hardness of water is due to sulphates and chlorides salt of calcium and magnesium ions. Permanent hardness of water cannot be removed by boiling. Substance like washing soda, calgon, and permutit process is used to remove permanent hardness of water.

Thus, the correct answer is 0.
Note:
Soaps are not advised to use in hard water which contains calcium and magnesium ions because it will not produce lather until all the calcium and magnesium ions have been precipitated.