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  4. Permanent hardness of water can be removed by which of the following process?

Q. Permanent hardness of water can be removed by which of the following process?

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Solution:

Washing soda removes both the temporary and permanent hardness by converting soluble calcium and magnesium compounds into insoluble carbonates.
$CaCl_{2}+Na_{2}CO_{3} \rightarrow CaCO_{3}+2NaCl$
$CaSO_{4}+Na_{2}CO_{3} \rightarrow CaCO_{3}+Na_{2}SO_{4}$
$Ca\left(\right.HCO_{3}\left(\left.\right)_{2}+Na_{2}CO_{3} \rightarrow CaCO_{3}+2NaHCO_{3}.$

Questions from NTA Abhyas 2022

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2. A cation is in the centre touches three anions. Assume that the anions also touch each other. The limiting radius ratio, $r^{+}/r^{-}$ is

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5. In a $10litre$ box $2.5mole$ hydroiodic acid is taken. After equilibrium $2HI\rightleftharpoonsH_{2}+I_{2}$ the concentration of $HI$ is found to be $0.1 \, \text{mol} \, \text{L}^{- 1}$ . The concentration of $\left[H_{2}\right]$ at equilibrium in $molL^{- 1}$ , is

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4. At standard conditions, if the change in the enthalpy for the following reaction is $-109 \,kJ\, mol^{-1}$ $H_{2(g)}+Br_{2(g)} \to 2HBr_{(g)}$ Given that bond energy of $H_{2}$ and $Br_{2}$ is $435\,KJ\,mol^{-1}$ and $192\,KJ\,mol^{-1}$ , respectively, what is the bond energy (in $KJ \,mol^{-1})$ of $HBr$ ?

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5. The density of 2 M aqueous solution of NaOH is 1.28 g/cm$^3$. The molality of the solution is
[Given that molecular mass of NaOH = 40 g mol$^{-1}$]

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