JEE 2013 :: Main 2013 :: Chemistry 2013

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For gaseous state, if most probable speed is denoted by C^*, average speed by  $\overline{C}$ and root square speed by C, then for a large number of molecules , the ratio s of these speeds are 

Answer:

Explanation:

$C^{*}$  = most probable speed=   $\sqrt{\frac{2RT}{M}}$

  speed= $\sqrt{\frac{8RT}{M}}$

C= mean square speed corrected as 

 rms= $\sqrt{\frac{3RT}{M}}$

$C^{*}$ <$\overline{C}$ <C

$C^{*}$:$\overline{C}$:C= 1 : $\sqrt{\frac{4}{\pi}}:\sqrt{\frac{3}{2}}$

                    =1:1.128:1.225

 As no option corresponds to mean square speed, it is understood as a misprint. It should be the root mean square speed

Arrange the following compounds in the order of decreasing acidity 

Answer:

Explanation:

 Electron releasing group decrease while electron-withdrawing group increases acidic strength by destabilising and stabilising the phenoxide ion formed respectively.

The molarity of a solution obtained by  mixing 750 ml. of  0.5 (M) HCl with 250 ml of 2(M) HCl will be

Answer:

Explanation:

$M_{f}=\frac{M_{1}V_{1}+M_{2}V_{2}}{V_{1}+V_{2}}$

  $=\frac{750\times0.5+250\times2}{750+250}=\frac{875}{1000}$

           =0.875 M

A piston filled with 0.04 mole of an ideal gas expands reversibly from 50.0 ml to 375 ml at a constant temperature of 37.0° , As it does so, it absorbs 208 J of heat. The values of q and W for the process will be (R=8.314 J/mol K, ln 7.5 =2.01)

Answer:

Explanation:

The process is isothermal  expansion, hence

 Q=-W

 $\triangle E=0$

 $W=2.303 nRT log \frac{V_{2}}{V_{1}}$

   $=2.303\times0.04\times 8.314 \times310 \times log \frac{335}{50}$

  =-208 J

 Q=+208J

w= -208 J (expansion work)

 Given,   $E^{0}_{Cr^{3+}/Cr}=-0.74 V$

 $E^{0}_{MnO_{4}^{-}/Mn^{2+}}=1.51 V$

$E^{0}_{Cr_{2}O_{7}^{2-}/Cr^{3+}}=1.33V$

$E^{0}_{{Cl}/Cl^{-}}=1.36V$

Based on the data given above strongest oxidising agent will be

Answer:

Explanation:

Higher the SRP_,   better is oxidising agent. Among the given   $E_{MnO_{4}/Mn^{2+}}^{+}$ is highest, hence MnO₄^- is the strongest oxidising agent

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• Main 2013 - Chemistry 2013
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