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Engineering
100 Views   |  

Which one of the alkali metals, forms only, the normal oxide, M_{2}O on heating in air?

  • Option 1)

    Rb

  • Option 2)

    K

  • Option 3)

    Li

  • Option 4)

    Na

 

Li

 

Engineering
96 Views   |  

In which of the following reactions, standard entropy change \left ( \Delta S^{o} \right ) is positive and standard Gibb's energy change \left ( \Delta G^{o} \right ) decreases sharply with increasing temperature?

  • Option 1)

    C\ graphite+\frac{1}{2}O_{2}\left ( g \right )\rightarrow CO\left ( g \right )

  • Option 2)

    CO\left ( g \right )+\frac{1}{2}O_{2}\left ( g \right )\rightarrow CO_2\left ( g \right )

  • Option 3)

    Mg\left (s \right )+\frac{1}{2}O_{2}\left ( g \right )\rightarrow MgO\left ( s \right )

  • Option 4)

    \frac{1}{2}C\ graphite+\frac{1}{2}O_{2}\left ( g \right )\rightarrow \frac{1}{2}CO_2\left ( g \right )

 
  Gibb's free energy (? G) -   - wherein Gibb's free energy enthalpy of reaction entropy temperature    C graphite + As amount of geseous substancance is increasing in product, thus is positive for this reaction, and we know that . As   is positive thus increase in tempreature will make more negative and will decrease. Option 1) Correct Option Option 2) Incorrect Option Option...
Engineering
135 Views   |  

Aluminium is extracted from alumina \left ( Al_{2}O_{3} \right )  by electrolysis of a molten mixture of:

  • Option 1)

    Al_{2}O_{3}+HF+N_{a}AlF_{4}

  • Option 2)

    Al_{2}O_{3}+CaF_{2}+N_{a}AlF_{4}

  • Option 3)

    Al_{2}O_{3}+Na_{3}AlF_{6}+CaF_{2}

  • Option 4)

    Al_{2}O_{3}+KF+Na_{3}AlF_{6}

 
As we learnt in concept Hall and Heroult Process - Use to extract aluminium. A fuse mixture of alumina (20%), cryolite (60%) and fluorspar (20%) is electrolysed using carbon electrodes. - wherein Cryolite makes Al2O3 conducting, fluorspar decreases the melting point of alumina    In Hall Heroult process, a fused mixture of alumina (20%) Al2O3, cryalite (60%) Na3AlF6, and flourspar (20%) CaF2 is...
Engineering
109 Views   |  

The enthalpy of fusion of water is 1.435 kCal/mol. The molar entropy change for the melting of ice at 0^{o}C is:

  • Option 1)

    10.52 cal/(molK)

  • Option 2)

    21.04 cal/(molK)

  • Option 3)

    5.260 cal/(molK)

  • Option 4)

    0.526 cal/(molK)

 
  Entropy for phase transition at constant pressure - - wherein Transition Fusion, Vaporisition, Sublimation Enthalpy Internal Energy Transitional temperature    molar entropy change=          Option 1) 10.52 cal/(molK) This solution is incorrect  Option 2) 21.04 cal/(molK) This solution is incorrect  Option 3) 5.260 cal/(molK) This solution is correct  Option 4) 0.526 cal/(molK) This...
Engineering
94 Views   |  

A car of mass m starts from rest and accelerates so that the instantaneous power delivered to the car has a constant magnitude P_{o}. The instantaneous velocity of this car is proportional to

  • Option 1)

    t^{2} P_{o}

  • Option 2)

    t^{1/2}

  • Option 3)

    t ^{-1/2}

  • Option 4)

    \frac{1}{\sqrt{m}}

 
As discussed in Power if the force is variable - - wherein     Option 1) This solution is incorrect Option 2) This solution is correct Option 3) This solution is incorrect Option 4) This solution is incorrect
Engineering
116 Views   |  

Which nomenclature is not according ti IUPAC system?

  • Option 1)

    Br-CH_{2}-CH= CH_{2}, 1-Bromo-prop-2-ene

  • Option 2)

  • Option 3)

  • Option 4)

 
As we learnt in Functional group -   -     IUPAC name : 3 - Bromopropene.   Option 1) Correct Option 2) Incorrect Option 3) Incorrect Option 4) Incorrect
Engineering
318 Views   |  

The moment of inertia of a uniform circular disc is maximum about an axis perpendicular to the disc and passing through

  • Option 1)

    B

  • Option 2)

    C

  • Option 3)

    D

  • Option 4)

    A

 

b

 

Engineering
163 Views   |  

ABC is an equilateral triangle with O as its centre. \vec{F}_{1},\: \vec{F}_{2},\: \vec{F}_{3} represent three forces acting along the sides AB, BC and AC respectively. If the total torque about O is zero the magnitude of \vec{F}_{3}

  • Option 1)

    F_{1}+F_{2}

  • Option 2)

    F_{1} - F_{2}

  • Option 3)

    \frac{F_{1}+F_{2}}{2}

  • Option 4)

    2(F_{1}+F_{2})

 
As discussed in Equilibrium -    Translational equilibrium        Rotational equilibrium -     Option 1) This option is correct. Option 2) This option is incorrect. Option 3) This option is incorrect. Option 4) This option is incorrect.
Engineering
419 Views   |  

Three masses are placed on the x-axis: 300 g at origin, 500 g at x=40 cm and 400 g at x=70 cm. The distance of the centre of mass from the origin is

  • Option 1)

    40 cm

  • Option 2)

    45 cm

  • Option 3)

    50 cm

  • Option 4)

    30 cm

 
As learnt in Centre of mass when some mass is added in the body - - wherein m1 &   are mass and position of centre of mass for whole body. m2 &  are mass and position of centre of mass of added mass.     Option 1) 40 cm This option is correct. Option 2) 45 cm This option is incorrect. Option 3) 50 cm This option is incorrect. Option 4) 30 cm This option is incorrect.
Engineering
165 Views   |  

If n1, n2 and n3 are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency n of the string is given by:

  • Option 1)

    \frac{1}{n}=\frac{1}{n_{1}}+\frac{1}{n_{2}}+\frac{1}{n_{3}}

  • Option 2)

    \frac{1}{\sqrt n}=\frac{1}{\sqrt n_{1}}+\frac{1}{\sqrt n_{2}}+\frac{1}{\sqrt n_{3}}

  • Option 3)

    \sqrt n= \sqrt n_{1}+\sqrt n_{2}+\sqrt n_{3}

  • Option 4)

    n =n_{1}+n_{2}+n_{3}

 
As we learnt in  Fundamental frequency with end correction -     (one end open)     (Both end open) e = end correction -   Option 1) Correct Option 2) Incorrect Option 3) Incorrect Option 4) Incorrect
Engineering
107 Views   |  

A circular platform is mounted on a frictionless vertical axle. Its radius R=2m and its moment of inertia about the axle is 200 kgm^{2}. It is initially at rest. A 50 kg man stands on the edge of the platform and begins to walk along the adge at the speed of 1 ms^{-1} relative to the ground. Time taken by the man to complete one revolution is

  • Option 1)

    \pi\:s

  • Option 2)

    \frac{3\pi}{2}\: s

  • Option 3)

    2\pi\: s

  • Option 4)

    \frac{\pi}{2}\: s

 
As discussed in Law of conservation of angular moment - - wherein If net torque is zero i.e. angular momentum is conserved only when external torque is zero.          (initial moment)  (final moment)   Option 1) This option is incorrect. Option 2) This option is incorrect. Option 3) This option is correct. Option 4) This option is incorrect.
Engineering
116 Views   |  

Two similar coils of radius r are lying concentrically with their planes at right angles to each others. The currents flowing in them are I \ and\ 2 I, respectively. The resultant magnetic field induction at  the centre will be:

  • Option 1)

    \frac{\sqrt{5}\mu_{o}I}{2R}

  • Option 2)

    \frac{{3}\mu_{o}I}{2R}

  • Option 3)

    \frac{\mu_{o}I}{2R}

  • Option 4)

    \frac{\mu_{o}I}{R}

 
  Magnetic field due to cCrcular Current Carrying arc - - wherein     Option 1) This option is correct  Option 2) This option is incorrect  Option 3) This option is incorrect  Option 4) This option is incorrect 
Engineering
87 Views   |  

An \alpha-particle moves in a circular path of radius 0.83cm in the presence of a magnetic field of  0.25 \ Wb/m^{2}. The wavelength associated with the particle will be:

  • Option 1)

    1\overset {o}{A}

  • Option 2)

    0.1\overset {o}{A}

  • Option 3)

    10\overset {o}{A}

  • Option 4)

    0.01\overset {o}{A}

 
  Radius of charged particle - -     Option 1) 1 This solution is incorrect  Option 2) 0.1 This solution is incorrect  Option 3) 10 This solution is incorrect  Option 4) 0.01 This solution is correct 
Engineering
265 Views   |  

The current (I) in the inductance is varying with time according to the plot shown in figure.

Which one of the following is the correct variation of voltage with time in the coil?

  • Option 1)

  • Option 2)