MHT CET 2018 :: Chemistry :: General questions

• Chemistry - General questions

The slope of the straight line obtained by plotting log₁₀k against 1/T represents what term?

Answer:

Explanation:

According to Arrhenius equation,

  $k= Ae^{-E_{a}/RT}$

 By taking log on both sides

$\log k= \log_{e}A-\frac{E_{a}}{RT}$

$\log_{10} k= \log_{10}A-\frac{E_{a}}{2.303RT}$

 Comparing it with y=mx+c

 A plot between log₁₀ k and ($\frac{1}{T}$) is a straight line and slope is given by

  Slope = $-\frac{E_{a}}{2.303R}$

                   ( slope has negative value)

Calculate the work done during combustion of 0.138 kg of ethanol, C₂H₅OH (l) at 300K.

Given: R=8.314 J K^-1 mol^-1, the molar mass of ethanol=46  g mol^-1.

Answer:

Explanation:

The combustion of ethanol , involves the following reaction, 

$C_{2}H_{5}OH(l)+3O_{2}(g)\rightarrow 2CO_{2}+3H_{2}O$

 Given, Mass of ethanol= 0.138 kg= 138 g

Temperature =300K

  R= 8.314 J K^-1 mol^-1

  Molar  mass of ethanol =46 g mol^-1

 No. of moles of ethanol = Mass of ethanol / Molar mass of ethanol

    = $\frac{138}{46}$=3

 Work done (W)  during combustion of 0.138 kg of  C₂H₅OH= nRT

       W=nRT

 W= 3 x 8.314 JK^-1 mol^-1 x 300 K

     W= 7482.6J

        =7482 J

 With which halogen the reactions of alkanes are explosive?

Answer:

Explanation:

The reaction of alkanes with fluorine are explosive. This is an explosive process that is difficult to control, so carried out in dark. In this process, the replacement of one or more hydrogen of alkane by halogen takes place. For this reaction the order of reactivity of halogen is 

I₂ < Br₂ < Cl₂ < F₂

 Lactic acid and glycollic acid are the monomers used for the preparation of polymer

Answer:

Explanation:

Dextron is a copolymer of glycolic acid  and lactic acid consisting of ester linkages that makes it biodegradable 

Nylon-2-nylon -6 is a copolymer of glycine

(H₂N-CH2-COOH) and aminocaproic acid  (H₂N(CH₂)₅ COOH) and is biodegradable in nature

. PHBV (poly-$\beta$- hydroxybutyrate- co- $\beta$-hydroxy valerate ) is obtained by copolymerisation of 3-hydroxybutyric acid and 3-hydroxy pentanoic acid.

. Buna-N is obtained by copolymerisation of 1,3 butadiene and acrylonitrile in the presence of peroxide catalyst.

Arenes on treatment with chlorine in presence of ferric chloride as a catalyst undergo what type of reaction?

Answer:

Explanation:

 Arenes on treatment with chlorine in presence of Lewis acid catalyst, ferric chloride or aluminium chloride and in the absence of light undergoes halogenation. It involves an electrophilic substitution  reaction

Mechanism of electrophilic substitution in as follows:

Step I: Generation of an electrophile.

  $Cl-Cl+AlCl_{3}\rightarrow Cl^{+}+Cl ^{\delta+}.........Al^{\delta-}-Cl_{3}$

                                                                 $\rightarrow Cl^{+}+[AlCl_{4}]^{-}$    Chloronium ion

Step II. Formation of carbocation (arenium ion)

The arenium ion gets stabilised by resonance

Step III  removal of proton

• Chemistry - General questions