MHT CET 2019 :: Chemistry :: General questions

• Chemistry - General questions

The molar conductivities at infinite dilution for sodium acetate, HCl and NaCl are 91 S cm² mol^-1,425.9 S cm² mol^-1  and 126.4 S cm² mol^-1  respectively. The molar conductivity of acetic acid at infinite dilution is 

Answer:

Explanation:

Key Idea Kohlraush law of independent  migration of ions can be used to calculate  $\wedge_{m}^{o}$ for weak electrolyte such as acetic acid 

Given,    $\wedge_{m(NaAC)}^{o}= 91$  $S cm^{2}mol^{-1}$

 $\wedge_{m(HCl)}^{o}$= 425.9 S $cm^{2}mol^{-1}$

 $\wedge_{m(NaCl)}^{o}= 126.4$ S $cm^{2}mol^{-1}$

 Using Kohlrausch law, to find the molar conductivity of acetic acid

$\wedge_{m(HAc)}^{o}= \lambda_{H^{+}}^{o}+\lambda_{AC^{-}}^{o}$

=$\lambda_{H^{+}}^{o}+\lambda_{Cl^{-}}^{o}+\lambda_{AC^{-}}^{o}+\lambda_{Na^{+}}^{o}-\lambda_{Cl^{-}}^{o}-\lambda_{Na^{+}}^{o}$

 =$\wedge_{m(HCl)}^{o}+\wedge_{m(NaAC)}^{o}-\wedge_{m(NaCl)}^{o}$

 ( 425.9+91.0-126.4) S cm² mol^-1

 = 390.5 S cm²   mol^-1

Which among the following  polymer does not  show cross linking in it?

Answer:

Explanation:

Nylon-6 polymer does not show cross linking  in it. It is a linear polymer. It is obtained by heating caprolactum with water at a high temperature . Structural  formula and name of given  polymer is shown below :

The effective atomic number of Iron (Z=26) in [Fe(CN)₆]^-3  is

Answer:

Explanation:

Key Idea 

 The total number of electrons that the central metal ion appears to possess in the complex including those gained by it in bonding is called the effective atomic number of the central metal ion.

 In the given complex ion [Fe(CN)₆]^3-  the Fe is in +3 oxidation state. As we know that an atomic number of iron is 26. The number of electron in Fe³⁺  is 23. Each of the  six cyanide molecules donates a pair of electrons so that EAN becomes

23+2 x6=35

In which among the following compounds oxidation number of nitrogen is +5 ?

Answer:

Explanation:

Oxidation number of nitrogen +5 in $HNO_{3}$

 1+ x+3 (-2)=0

x-5=0

x= + 5

A gas performs 0.20 kJ work on surrounding and absorbs  120 J  of heat from the surrounding. Hence, change in internal energy is 

Answer:

Explanation:

According to first law of thermodynamics,

 $\triangle$ U= q+w

 Since, work done on the surrounding.

 So, W= -0.320 kJ

  =-320 J

 q=120J

 $\therefore$   $\triangle$ U= -320+120

                                     =-200 J

• Chemistry - General questions