Calculate the temporary and permanent hardness of water sample having the following the following constituents per litre:\$ Ca(HCO_{3})_{2} = 162\, mg, MgCl_{2} = 95 =\, mg, \$\$ NaCl = 585\, mg, Mg(HCO_{3})_{2} = 73\, mg, \$\$ CaSO_{4} = 136\, mg \$

mole of \$ Ca(HCO_{3})_{2} = \dfrac{162\times 10^{-3}mg}{162\,g/mole} = 1\times 10^{-3}\,moles \$Mole of \$ Ca(SO_{4}) = \dfrac{136\times 10^{-3}g}{136\,g/mole} = 1\times 10^{3}\,mole \$Total mole of \$ Ca = 2\times 10^{-3}\,mole \$mass of \$ CaCO_{3} = 2\times 10^{-3}\times 100 = 0.2\,g \$\$ \therefore \$ ppm (permanent hardness) \$ = \dfrac{6.2}{1000}\times 10^{6} = 200\,ppm \$Mole of \$ MgCl_{2} = \dfrac{95\times 10^{-3}}{95} = 1\times 10^{-3}\,mole \$ Mole Mg \$ (HCg)_{2} = \dfrac{73\times 10^{-3}}{146} = 5\times 10^{-4}\,mole \$mole Mg \$ = 1.5\times 10^{-4}\,mole \$Mole g \$ CaCO_{3} \$ (In terms of mg) \$ = 1.5\times 10^{-3} \$mass \$ = 1.5\times 10^{-3} = 0.150\,g \$ppm (temporary hardness) \$ = \dfrac{0.150}{100}\times 106 = 150\,ppm \$Hence, the correct option is \$\text{C}\$

What causes the temporary and permanent hardness of water ?

The presence of calcium and magnesium bicarbonates \$Ca(HCO_3)_2\$ and \$Mg(HCO_3)_2\$ causes temporary hardness in water. The presence of soluble salts of calcium and magnesium, i.e., sulphates and chlorides of calcium and magnesium cause permanent hardness in water.

Write chemical reactions to show the amphoteric nature of water.

Amphoteric nature of water is represented by following chemical reactions.(1) Water as a base:\$\displaystyle H_2O(l)+H_2S(g) \rightleftharpoons H_3O^+(aq) + HS^-(aq) \$(2) Water as an acid:\$\displaystyle H_2O(l) + NH_3(aq) \rightleftharpoons OH^-+NH_4^+ \$(3) Self ionization of water in which water simultaneous acts as acid and base.\$\displaystyle 2H_2O \rightarrow H_3O^+ + OH^- \$

Pressure cooker reduces cooking time because:

Because under pressure, the heat builds faster and maintains temperature better, so cooking time is reduced. ... The increased pressure inside the cooker increases the boiling point of water above \$100 ^0C\$ so more cooking is done before the water actually starts to boil. So ultimately food is cooked faster.

Permanent hardness can be removed by simple boiling it.

Permanent hardness is caused by the presence of sulfates of \$Ca/Mg\$. Which further increases the hardness on boiling because boiling removes only water in the form of vapour while none of its mineral content boil away-they remain in the vessel.

Which of the following methods is used for the removal of temporary hardness of water?

In Clark's process, slaked lime,\$ Ca(OH)_2\$ is added to temporary hard water. Insoluble calcium carbonate precipitates out and no longer produce hardness.Clark's process involves the addition of a controlled quantity of slaked lime (calcium hydroxide)\$ Ca(HCO_3)_2(aq) + Ca(OH)_2(aq)\rightarrow 2CaCO_3(s) + 2H_2O(l)\$ \$Mg(HCO_3)_2(aq) + Ca(OH)_2(aq)\rightarrow CaCO_3(s) + MgCO_3(s) + 2H2O(l)\$Slaked lime is itself a source of calcium ions (and hence hardness) so care must be taken to avoid adding an excess.

The formula of calgon is:

The formula of calgon is \$Na_2[Na_4(PO_3)_6]\$. Calgon is a trade name of a complex salt, sodium hexametaphosphate \$(NaPO_3)_6\$. It is used for softening hard water. Calgon ionizes to give a complex anion.

When temporary hard water containing \$ Mg(HCO_{3})_{2} \$ is boiled, the ppt. formed is of

\$ Mg(OH)_{2} \$ is less soluble than \$ MgCO_{3} \$. On boiling temporary hard water containing \$ Mg^{2+} \$ ions, the ppt. obtained is of \$ Mg(OH)_{2} \$ and not that of \$ MgCO_{3} \$.\$MgCO_3+H_2O\xrightarrow{\Delta} Mg(OH)_2\downarrow+CO_2\$

The hardness of a water sample containing \$10^{-3}\$M \$MgSO_4\$ expressed as \$CaCO_3\$ equivalents (in ppm) is ________. [molar mass of \$MgSO_4\$ is \$120.37\$ g/mol]

\$10^{-3}\$ molar \$MgSO_4 = 10^{-3}\$ moles of \$MgSO_4\$ present in \$1\$ Litre.\$n_{CaCO_3} =n_{MgSO_4} \$\$PPM\$ (in term of \$CaCO_3) = \dfrac{10^{-3}\times 100}{1000} \times 10^6\$ \$= 100\ ppm\$

What do you understand by the term 'auto-protolysis' of water? What is its significance?

The reaction between two water molecules to produce hydronium ion and hydroxide ion is known as autoprotolysis of water. This is self ionization of water.\$\displaystyle 2H_2O \rightarrow H_3O^++OH^- \$ This reaction indicates the amphoteric nature of water. It can act as an acid as well as a base. One water molecule donates electron whereas other water molecule accepts electron.

Hard and Soft Water-Advanced | Definition, Examples, Diagrams

definition

Hard and soft water

Hard water: Water that contain high amout of dissolved minerls or ions such as calcium, magnesium etc.
Soft water: Soft water is surface water that contains very low concentration of ions or minerals, e.g., Rainwater and distilled water.

definition

Causes and types of hardness of water

Hardness of water is due to the chlorides, sulphates bicarbonates of calcium and magnesium in it.
Types of hardness of water are:

Temporary hardness
Permanent hardness

definition

Methods of removing temporary hardness

Temporary hardness can be removed by boiling and filtering the water.

Boiling : When temporary water is boiled, bicarbonates of calcium and magnesium decompose to form insoluble calcium and magnesium carbonates which can be easily filtered off
By clark's process:

C a O + H_{2} O \to C a (O H)_{2}

C a (H C O_{3})_{2} + C a (O H)_{2} \to 2 C a C O_{3} + 2 H_{2} O

definition

Methods to remove permanent hardness

Washing soda process: Hard water is treated with a calculated amount of washing soda when chlorides and sulphates of calcium and magnesium present in hard water get precipitated as insoluble calcium and magnesium carbonates which can be filtered off.

C a C l_{2} + N a_{2} C O_{3} \to C a C O_{3} + 2 N a C l

M g S O_{4} + N a_{2} C O_{3} \to M g C O_{3} + N a_{2} S O_{4}

Calgon's method: Sodium hexametaphosphate (

N_{6} P_{6} O_{18}

), commercially called 'calgon', when added to hard water , the reaction is as follows:-

N a_{6} P_{6} O 18 \to N a^{+} + N a_{4} P_{6} O_{18}^{2 -}

(M = Mg, Ca)

M^{2 +} + N a_{4} P_{6} O_{18}^{2 -} \to [N a_{2} M P_{6} O_{18}]^{2 -} + 2 N a^{+}

The complex anion keeps the

M g^{2 +}

and

C a^{2 +}

ions in solution.

definition

Experiments based on hard and soft water

There are two types of hardness i.e. temporary hardness and Permanent hardness. Temporary hardness is due to calcium and magnesium bicarbonates. It can be removed by boiling followed by filtration. Permanent hardness is due to the presence of chlorides and sulfates of calcium and magnesium. It can be removed by the addition of washing soda and caustic soda.

definition

Methods for removing both the hardness of water

Lime Soda process

C a (H C O_{3})_{2} + C a (O H)_{2} \to 2 C a C O_{3} + 2 H_{2} O

C a C l_{2} + N a_{2} C O_{3} \to C a C O_{3} + 2 N a C l

Ion exchange method: This is the most modern method for softening of hard water. $C a^{2 +}, M g^{2 +}$ ions present in hard water are exchanged by those present in complex inorganic and organic compounds.

example

Removal of temporary and permanent hardness by ion exchange method

There are a number of methods to remove the hardness present in water. A few methods to remove hardness from water are,

Chemical Process of Boiling Hard Water
Adding Slaked Lime (Clark's Process)
Adding Washing Soda
Calgon Process
Ion Exchange Process
Using Ion Exchange Resins

example

Removal of hardness of water

There are a number of methods to remove the hardness present in water. A few methods to remove hardness from water are,

Chemical Process of Boiling Hard Water
Adding Slaked Lime (Clark's Process)
Adding Washing Soda
Calgon Process
Ion Exchange Process
Using Ion Exchange Resins

example

Removal of hardness of water

There are a number of methods to remove the hardness present in water. A few methods to remove hardness from water are,

Chemical Process of Boiling Hard Water
Adding Slaked Lime (Clark's Process)
Adding Washing Soda
Calgon Process
Ion Exchange Process
Using Ion Exchange Resins

example

Removal of hardness of water

There are a number of methods to remove the hardness present in water. A few methods to remove hardness from water are,

Chemical Process of Boiling Hard Water
Adding Slaked Lime (Clark's Process)
Adding Washing Soda
Calgon Process
Ion Exchange Process
Using Ion Exchange Resins

definition

Properties of Water

Properties of water:

Water is transparent in colour.
Water has no shape,it takes the shape of vessel in which it is kept.
Water applies an upward force on every object immersed in it.
Water could dissolve many things like salt, sugar but not oil and chalk powder.
In water few objects sinks and few floats based on the heaviness and area occupied by objects.For example, a needle sinks and a heavy boat floats , this happens because boats occupies more area over water and needle occupies less area creating more push on water.

Hard and Soft Water-Advanced

definition

Hard and soft water

definition

Causes and types of hardness of water

definition

Methods of removing temporary hardness

definition

Methods to remove permanent hardness

definition

Experiments based on hard and soft water

definition

Methods for removing both the hardness of water

example

Removal of temporary and permanent hardness by ion exchange method

example

Removal of hardness of water

example

Removal of hardness of water

example

Removal of hardness of water

definition

Properties of Water

REVISE WITH CONCEPTS

Water - Structure and Physical Properties

Water - Chemical Properties

Calculate the temporary and permanent hardness of water sample having the following the following constituents per litre:
$C a (H C O_{3})_{2} = 162 m g, M g C l_{2} = 95 = m g,$
$N a C l = 585 m g, M g (H C O_{3})_{2} = 73 m g,$
$C a S O_{4} = 136 m g$

What causes the temporary and permanent hardness of water ?

Write chemical reactions to show the amphoteric nature of water.

Pressure cooker reduces cooking time because:

Permanent hardness can be removed by simple boiling it.

Which of the following methods is used for the removal of temporary hardness of water?

The formula of calgon is:

When temporary hard water containing $M g (H C O_{3})_{2}$ is boiled, the ppt. formed is of

The hardness of a water sample containing $1 0^{- 3}$ M $M g S O_{4}$ expressed as $C a C O_{3}$ equivalents (in ppm) is ________.

[molar mass of $M g S O_{4}$ is $120.37$ g/mol]

What do you understand by the term 'auto-protolysis' of water? What is its significance?

definition

Hard and soft water

definition

Causes and types of hardness of water

definition

Methods of removing temporary hardness

definition

Methods to remove permanent hardness

definition

Experiments based on hard and soft water

definition

Methods for removing both the hardness of water

example

Removal of temporary and permanent hardness by ion exchange method

example

Removal of hardness of water

example

Removal of hardness of water

example

Removal of hardness of water

definition

Properties of Water

REVISE WITH CONCEPTS

Water - Structure and Physical Properties

Water - Chemical Properties

Calculate the temporary and permanent hardness of water sample having the following the following constituents per litre: Ca(HCO3​)2​=162mg,MgCl2​=95=mg, NaCl=585mg,Mg(HCO3​)2​=73mg, CaSO4​=136mg

What causes the temporary and permanent hardness of water ?

Write chemical reactions to show the amphoteric nature of water.

Pressure cooker reduces cooking time because:

Permanent hardness can be removed by simple boiling it.

Which of the following methods is used for the removal of temporary hardness of water?

The formula of calgon is:

When temporary hard water containing Mg(HCO3​)2​ is boiled, the ppt. formed is of

The hardness of a water sample containing 10−3M MgSO4​ expressed as CaCO3​ equivalents (in ppm) is ________. [molar mass of MgSO4​ is 120.37 g/mol]

What do you understand by the term 'auto-protolysis' of water? What is its significance?

Calculate the temporary and permanent hardness of water sample having the following the following constituents per litre:
$C a (H C O_{3})_{2} = 162 m g, M g C l_{2} = 95 = m g,$
$N a C l = 585 m g, M g (H C O_{3})_{2} = 73 m g,$
$C a S O_{4} = 136 m g$

When temporary hard water containing $M g (H C O_{3})_{2}$ is boiled, the ppt. formed is of

The hardness of a water sample containing $1 0^{- 3}$ M $M g S O_{4}$ expressed as $C a C O_{3}$ equivalents (in ppm) is ________.

[molar mass of $M g S O_{4}$ is $120.37$ g/mol]