MHT CET 2017 :: Chemistry :: General questions

• Chemistry - General questions

 The conversion of ethyl bromide using  sodium and dry acetone , this reaction is known as

Answer:

Explanation:

 Alkyl iodides and fluorides are prepared by the S_N2 mechanism. Alkyl chlorides or bromides reacts with Nal in dry acetone to given alkyl iodine. This reaction is known as Finkelstein reaction.

$R-X+Nal\rightarrow Rl+NaX[X=Cl,Br]$

e.g,  $C_{2}H_{5}Br+Nal\rightarrow C_{2}H_{5}l+NaBr$

The first law of thermodynamics for isothermal process is 

Answer:

Explanation:

According to firsr law of thermodynamics

$\triangle U= q+w$

where, $\triangle U$  = internal energy

 q=  Heat, w= work done

 For isothermal process, $\triangle T$=0 , $\triangle U$=0

   q=-w

Which among the following equation represents the Arrhenius equation?

Answer:

Explanation:

Variation  of rate constant k with temperature T(K) is given by Arrhenius equation

It is based  on the two theories of reaction rates, 

i.e, collision theory and transition state theory.

$k=Ae^{-E_{a}/RT}=\frac{A^-}{e^{E_{a}/RT}}$  .........(i)

 where 'A'  is called the frequency factor or pre-exponential factor.

 E_a is activation energy  $e^{-E_{a}/RT}$ is referred as Boltzmann factor. A, has same unit as the rate constant. Collectively A and E_a are called  the  Arrhenius parameters  of the reaction 

Which among the following reactions is an example of pseudo first-order reaction?

Answer:

Explanation:

The reactions in which the molecularity is two but they confirm  to the first order are known as pseudo  first order  reaction or pseudo unimolecular reactions.

 e.g, inversion of cane sugar

$C_{12}H_{22}O_{11}+H_{2}O$  $\underrightarrow{H^{+}}$     $C_{6}H_{12}O_{6}+C_{6}H_{12}O_{6}$

Sucrose(cane sugar)                                      Glucose    Fructose

The concentration of water remains constant

The correct charge on and co-ordination number of 'Fe' on K₃ [Fe(CN)₆] is 

Answer:

Explanation:

Coordination number of Fe in K₃ [Fe(CN)₆] is 6 because it is bonded with six CN ligands .

Let x be the oxidation state of Cr

$\therefore$      x+6(-1)=-3

$\therefore$   x=+3

• Chemistry - General questions