MCQ
Anhydrous borax is:
  • $ \mathrm{Na}_2 \mathrm{~B}_4 \mathrm{O}_7 $
  • B
    $\mathrm{Na}_2 \mathrm{~B}_4 \mathrm{O}_7 \cdot 5 \mathrm{H}_2 \mathrm{O} $
  • C
    $ \mathrm{Na}_2 \mathrm{~B}_4 \mathrm{O}_7 \cdot 10 \mathrm{H}_2 \mathrm{O} $
  • D
    $ \mathrm{Na}_2 \mathrm{~B}_4 \mathrm{O}_7 \cdot 8 \mathrm{H}_2 \mathrm{O} $

Answer

Correct option: A.
$ \mathrm{Na}_2 \mathrm{~B}_4 \mathrm{O}_7 $
Anhydrous borax has formula $ \mathrm{Na}_2 \mathrm{~B}_4 \mathrm{O}_7 $​.
Anhydrous means no water of crystallisation.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

The amount of energy required to break a bond is same as the amount of energy released when the same bond is formed. In gaseous state, the energy required for homolytic cleavage of a bond is called Bond Dissociation Energy ($BDE$) or Bond Strength. BDE is affected by s-character of the bond and the stability of the radicals formed. Shorter bonds are typically stronger bonds. BDEs for some bonds are given below :

$\begin{array}{l} Cl - Cl ( g ) \longrightarrow Cl ^*( g )+ Cl ^*( g ) \Delta H ^{\circ}=58 kcal mol ^{-1} \\ H _3 C - Cl ( g ) \longrightarrow H _3 C ^*( g )+ Cl ^{\circ}( g ) \Delta H ^{\circ}=85 kcal mol ^{-1} \\ H - Cl ( g ) \quad \longrightarrow H ^*( g ) \quad+ Cl ^*( g ) \Delta H ^{\circ}=103 kcal mol ^{-1} \\\end{array}$

($1$) Correct match of the $C - H$ bonds (shown in bold) in Column $J$ with their BDE in Column $K$ is

Column $J$ Molecule

Column $K$ $\operatorname{BDE}( kcal mol -1)$

$(P)$ $H - C H \left( CH _3\right)_2$ ${ (i) } 132$
$(Q)$ $H - CH _2 Ph$ ${ (ii) } 110$
$(R)$ $H - C H = CH _2$ ${ (iii) } 95$
$(S)$ $H - C \equiv CH$ ${ (iv) } 88$

$(A)$ $P - iii, Q - iv, R - ii, S - i$

$(B)$ $P - i, Q - ii, R - iii, S - iv$

$(C)$ $P - iii, Q - ii, R - i, S - iv$

$(D)$ $P - ii, Q - i, R - iv, S - iii$

($2$) For the following reaction

$CH _4( g )+ Cl _2( g ) \xrightarrow{\text { light }} CH _3 Cl ( g )+ HCl ( g )$

the correct statement is

$(A)$ Initiation step is exothermic with $\Delta H ^{\circ}=-58 kcal mol ^{-1}$

$(B)$ Propagation step involving ${ }^{\circ} CH _3$ formation is exothermic with $\Delta H ^{\circ}=-2 kcal mol ^{-1}$.

$(C)$ Propagation step involving $CH _3 Cl$ formation is endothermic with $\Delta H ^{\circ}=+27 kcal mol ^{-1}$.

$(D)$ The reaction is exothermic with $\Delta H ^{\circ}=-25 kcal mol ^{-1}$.

The mole fraction of urea in an aqueous urea solution containing $900 g$ of water is $0.05$ . If the density of the solution is $1.2 g cm ^{-3}$, the molarity of urea solution is. . . . . (Given data : Molar masses of urea and water are $60 g mol ^{-1}$ and $18 g mol ^{-1}$, respectively)
Oils are converted into fats by
Reaction of $HBr$ with propene in the presence of peroxide gives
Which statement is correct ?
When $17\,g$ of $H_2A$ (dibasic acid) completely neutralised with $100\,mL,\,\,1\,M\,BOH$ (monoacidic base) then molecular weight of acid is
The values of ${K_{sp}}$for $CuS,\,\,A{g_2}S$ and $HgS$ are ${10^{ - 31}},\,{10^{42}}$ and ${10^{ - 54}}$ respectively. The correct order of their solubility in water is
The amount of $BaSO_4$ formed upon mixing $100\,mL$ of $20.8\%$ $BaCl_2$ solution with $50\,mL$ of $9.8\%$ $H_2SO_4$ solution will be ............. $\mathrm{g}$

( $Ba = 137,\,\,Cl = 35.5,\,\,S = 32,\,\,H = 1$ and $O = 16$ )

In $Xe{F_4}$ hybridization is
The number of radial nodes of $3s$ and $2p$ orbitals are respectively