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JEE Main 201912 AprilEvening Shift
Exam
JEE Main
Year
2019
Date
12 April
Shift
Evening Shift
Subject
Chemistry
Chapter
Hydrogen

JEE Main 2019 · 12 April · Evening Shift · Chemistry · Hydrogen

The temporary hardness of a water sample is due to compound X ....

The temporary hardness of a water sample is due to compound X.X . Boiling this sample converts XX to compound Y.Y . XX and Y,Y, respectively, are:

Options

  1. AMg{\left(HC{O}_{3}\right)}_{2} and MgCO3MgC{O}_{3}
  2. BCa(HCO3)2Ca{\left(HC{O}_{3}\right)}_{2} and Ca(OH)2Ca{\left(OH\right)}_{2}
  3. CMg(HCO3)2Mg{\left(HC{O}_{3}\right)}_{2} and Mg(OH)2Mg{\left(OH\right)}_{2}
  4. DCa( HC O3)Ca{\left(\text{ HC }{O}_{3}\right)}_{2}andandCaO

Correct answer

C. Mg(HCO3)2Mg{\left(HC{O}_{3}\right)}_{2} and Mg(OH)2Mg{\left(OH\right)}_{2}

Step-by-step solution

Both Mg(HCO3)2Mg{\left(HC{O}_{3}\right)}_{2} and Ca(HCO3)2Ca{\left(HC{O}_{3}\right)}_{2} are responsible for temporary hardness.
Mg(HCO3)2(X)→Boiling2MgCO3↓+CO2↑+H2O\mathop{\text{Mg}{\left(\text{HC}{\text{O}}_{3}\right)}_{2}}_{\left(X\right)}\overset{\text{Boiling}}{\to}\text{2MgC}{\text{O}}_{3} ↓ + \text{C}{\text{O}}_{2} ↑ + {H}_{2}O
CO3−2+H2O→HCO3−+OH−\text{C}{\text{O}}_{3}^{- 2} + {H}_{2}O \to \text{HC}{\text{O}}_{3}^{-} + \text{O}{\text{H}}^{-}
Mg+2+2OH−→Mg(OH)2(Y)\text{M}{\text{g}}^{+ 2} + 2\text{O}{\text{H}}^{-} \to \mathop{\text{Mg}{\left(\text{OH}\right)}_{2}}_{( Y )}
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