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.

Water - Structure and Physical Properties | Definition, Examples, Diagrams

definition

Physical properties of water

Some physical properties of water are: pure water is colourless, odourless and tasteless liquid, it freezes at 0

^{o}

C and boils at 100

^{o}

C under 1 atm pressure. Water is a non-conductor of electricity and heat. The density of the water at 4

^{o}

C is 1 g/ml. Water is neutral to litmus.

definition

Structure of water

Water has three dimensional structure in which central oxygen is bonded to two hydrogen atom.The hybridization of oxygen is

s p^{3}

definition

Hydrogen bonding in water and ice

In water hydrogen bonds are formed between two Hydrogen

(H)

and electronegative

(O)

Oxygen atom, the bonding is intra molecular Hydrogen bonding because it is formed between the hydrogen and oxygen atom which is present in same molecule.

definition

Boiling point of water

Water

(H_{2} O)

is a polar, universal solvent. Liquid at room temperature and boils at

10 0^{0} C

definition

Freezing point of water

The freezing point of water is 32 degrees Fahrenheit, or zero degrees Celsius. The freezing temperature of water also equals the melting temperature of ice.

definition

Uses of water

Water is used for photosynthesis by plants, drinking, bathing, washing, cooking by humans and also in industries.

example

surface tension of water

The cohesive force between liquid molecules is responsible for the phenomenon known as surface tension. The molecules at the surface of water do not have other water molecules on all sides of them and hence they cohere more strongly to those directly associated with them,

Water - Structure and Physical Properties

definition

Physical properties of water

definition

Structure of water

definition

Hydrogen bonding in water and ice

definition

Boiling point of water

definition

Freezing point of water

definition

Uses of water

example

surface tension of water

REVISE WITH CONCEPTS

Water - Chemical Properties

Hard and Soft Water-Advanced

Quick Summary With Stories

Structure of Water and Ice

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

Physical properties of water

definition

Structure of water

definition

Hydrogen bonding in water and ice

definition

Boiling point of water

definition

Freezing point of water

definition

Uses of water

example

surface tension of water

REVISE WITH CONCEPTS

Water - Chemical Properties

Hard and Soft Water-Advanced

Quick Summary With Stories

Structure of Water and Ice

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]