Answer
Verified
414k+ views
- Hint: Temporary hardness of water is caused by the bicarbonates of Magnesium (atomic number 12 ) and Calcium (atomic number 20).
Complete step by step answer:
Temporary hardness is because of the presence of bicarbonates of calcium and magnesium. Rainwater dissolves small quantities of \[C{{O}_{2}}\] from the atmosphere, forming a very dilute solution of carbonic acid. This water attacks calcium and magnesium carbonates in any rocks over which it flows, and the soluble hydrogen carbonates or bicarbonates are formed.
$CaC{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}\overset{{}}{ \Leftrightarrow}Ca{{(HC{{O}_{3}})}_{2}}$
Temporary hardness in water is easily removed by boiling, as the bicarbonates decompose readily and the insoluble carbonates are precipitated.
\[M{{g}^{2+}}(aq)+2{{C}_{17}}{{H}_{35}}CO{{O}^{-}}(aq)\xrightarrow{{}}{{({{C}_{17}}{{H}_{35}}COO)}_{2}}Mg\]
\[Ca{{(HC{{O}_{3}})}_{2}}\xrightarrow{boil}CaC{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}\]
(insoluble)
\[Mg{{(HC{{O}_{3}})}_{2}}\xrightarrow{boil}MgC{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}\]
(insoluble)
Temporary hardness can also be removed by Clark’s process which involves the addition of slaked lime \[[Ca{{(OH)}_{2}}]\].
\[Ca{{(HC{{O}_{3}})}_{2}}+Ca{{(OH)}_{2}}\xrightarrow{{}}2CaC{{O}_{3}}+2{{H}_{2}}O\]
(insoluble)
\[Mg{{(HC{{O}_{3}})}_{2}}+Ca{{(OH)}_{2}}\xrightarrow{{}}\{2CaC{{O}_{3}}+Mg{{(OH)}_{2}}\}+2{{H}_{2}}O\]
(insoluble)
It is essential to add only the calculated amount of \[Ca{{(OH)}_{2}}\]because the excess will cause artificial hardness.
Therefore, we conclude that the temporary hardness of water is caused by Calcium Hydrogen Carbonate. So Option D is the correct answer.
Additional Information: Water is said to be soft if it produces sufficient lather with the soap, and water is described as being hard if it forms an insoluble scum before it forms a lather with the soap. The hardness of water is because of the presence of salts in water. The hardness of natural water is generally caused by the bicarbonates and sulphates of calcium and magnesium, but in fact, all soluble salts that form a scum with the soap cause hardness.
\[C{{a}^{2+}}(aq)+2{{C}_{17}}{{H}_{35}}CO{{O}^{-}}(aq)\xrightarrow{{}}{{({{C}_{17}}{{H}_{35}}COO)}_{2}}Ca\]
\[M{{g}^{2+}}(aq)+2{{C}_{17}}{{H}_{35}}CO{{O}^{-}}(aq)\xrightarrow{{}}{{({{C}_{17}}{{H}_{35}}COO)}_{2}}Mg\]
(Anion of Soap) (Insoluble Precipitates)
Soap will not produce a lather with water until all the calcium and magnesium ions have been precipitated. Using hard water thus results in the wastage of soap. Hence, in our household, we use soft water for all purposes. This also saves us from wastage of water.
Note: Permanent hardness of water is caused by the soluble salts of magnesium and calcium when present in the form of chlorides and sulfides in water. The permanent hardness of water cannot be removed by boiling. To remove permanent hardness of water we need to treat the water with washing soda.
Complete step by step answer:
Temporary hardness is because of the presence of bicarbonates of calcium and magnesium. Rainwater dissolves small quantities of \[C{{O}_{2}}\] from the atmosphere, forming a very dilute solution of carbonic acid. This water attacks calcium and magnesium carbonates in any rocks over which it flows, and the soluble hydrogen carbonates or bicarbonates are formed.
$CaC{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}\overset{{}}{ \Leftrightarrow}Ca{{(HC{{O}_{3}})}_{2}}$
Temporary hardness in water is easily removed by boiling, as the bicarbonates decompose readily and the insoluble carbonates are precipitated.
\[M{{g}^{2+}}(aq)+2{{C}_{17}}{{H}_{35}}CO{{O}^{-}}(aq)\xrightarrow{{}}{{({{C}_{17}}{{H}_{35}}COO)}_{2}}Mg\]
\[Ca{{(HC{{O}_{3}})}_{2}}\xrightarrow{boil}CaC{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}\]
(insoluble)
\[Mg{{(HC{{O}_{3}})}_{2}}\xrightarrow{boil}MgC{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}\]
(insoluble)
Temporary hardness can also be removed by Clark’s process which involves the addition of slaked lime \[[Ca{{(OH)}_{2}}]\].
\[Ca{{(HC{{O}_{3}})}_{2}}+Ca{{(OH)}_{2}}\xrightarrow{{}}2CaC{{O}_{3}}+2{{H}_{2}}O\]
(insoluble)
\[Mg{{(HC{{O}_{3}})}_{2}}+Ca{{(OH)}_{2}}\xrightarrow{{}}\{2CaC{{O}_{3}}+Mg{{(OH)}_{2}}\}+2{{H}_{2}}O\]
(insoluble)
It is essential to add only the calculated amount of \[Ca{{(OH)}_{2}}\]because the excess will cause artificial hardness.
Therefore, we conclude that the temporary hardness of water is caused by Calcium Hydrogen Carbonate. So Option D is the correct answer.
Additional Information: Water is said to be soft if it produces sufficient lather with the soap, and water is described as being hard if it forms an insoluble scum before it forms a lather with the soap. The hardness of water is because of the presence of salts in water. The hardness of natural water is generally caused by the bicarbonates and sulphates of calcium and magnesium, but in fact, all soluble salts that form a scum with the soap cause hardness.
\[C{{a}^{2+}}(aq)+2{{C}_{17}}{{H}_{35}}CO{{O}^{-}}(aq)\xrightarrow{{}}{{({{C}_{17}}{{H}_{35}}COO)}_{2}}Ca\]
\[M{{g}^{2+}}(aq)+2{{C}_{17}}{{H}_{35}}CO{{O}^{-}}(aq)\xrightarrow{{}}{{({{C}_{17}}{{H}_{35}}COO)}_{2}}Mg\]
(Anion of Soap) (Insoluble Precipitates)
Soap will not produce a lather with water until all the calcium and magnesium ions have been precipitated. Using hard water thus results in the wastage of soap. Hence, in our household, we use soft water for all purposes. This also saves us from wastage of water.
Note: Permanent hardness of water is caused by the soluble salts of magnesium and calcium when present in the form of chlorides and sulfides in water. The permanent hardness of water cannot be removed by boiling. To remove permanent hardness of water we need to treat the water with washing soda.
Recently Updated Pages
Basicity of sulphurous acid and sulphuric acid are
Three beakers labelled as A B and C each containing 25 mL of water were taken A small amount of NaOH anhydrous CuSO4 and NaCl were added to the beakers A B and C respectively It was observed that there was an increase in the temperature of the solutions contained in beakers A and B whereas in case of beaker C the temperature of the solution falls Which one of the following statements isarecorrect i In beakers A and B exothermic process has occurred ii In beakers A and B endothermic process has occurred iii In beaker C exothermic process has occurred iv In beaker C endothermic process has occurred
What is the stopping potential when the metal with class 12 physics JEE_Main
The momentum of a photon is 2 times 10 16gm cmsec Its class 12 physics JEE_Main
How do you arrange NH4 + BF3 H2O C2H2 in increasing class 11 chemistry CBSE
Is H mCT and q mCT the same thing If so which is more class 11 chemistry CBSE
Trending doubts
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
Two charges are placed at a certain distance apart class 12 physics CBSE
Difference Between Plant Cell and Animal Cell
What organs are located on the left side of your body class 11 biology CBSE
Change the following sentences into negative and interrogative class 10 english CBSE
The planet nearest to earth is A Mercury B Venus C class 6 social science CBSE
The Equation xxx + 2 is Satisfied when x is Equal to Class 10 Maths
What is BLO What is the full form of BLO class 8 social science CBSE