Tag: physics

Questions Related to physics

The size of container B is double that of A and gas in B is at double the temperature and pressure than that in A. The ratio of molecules in the two containers will then be -

real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

  1. $\frac{N _B}{N _A} = \frac{1}{1}$

  2. $\frac{N _B}{N _A} = \frac{2}{1}$

  3. $\frac{N _B}{N _A} = \frac{4}{1}$

  4. $\frac{N _B}{N _A} = \frac{1}{2}$

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Correct Option: A

Two vertical parallel glass plates are partially submerged in water. The distance between the plates is $d = 0.10 mm$, and their width is $l  = 12 cm$. Assuming that the water between the plates does not reach the upper edges of the plates and that the wetting is complete, find the force of their mutual attraction.

real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

  1. $17N$

  2. $13N$

  3. $10$

  4. $19N$

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Correct Option: B

For gaseous decomposition of ${PCI} _{5}$ in a closed vessel the degree of dissociation '$\alpha $', equilibrium pressure 'P' & ${'K} _{p}'$ are related as

real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

  1. $\ \alpha =\sqrt { \frac { { K } _{ p } }{ P } } $

  2. $\ \alpha =\frac { 1 }{ \sqrt { { K } _{ p }+P } } $

  3. $\ \alpha =\sqrt { \frac { { K } _{ p }+P }{ { K } _{ p } } } $

  4. $\alpha =\sqrt { { K } _{ p }+P } $

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Correct Option: A
Explanation:

${  \quad \quad \quad \quad \quad \quad \quad PCl } _{ 5 }\rightleftharpoons { PCl } _{ 3(9) }+{ Cl } _{ 2(9) }\\ Initial\quad mole\quad \quad \quad 1\quad  \quad 0\quad\quad\quad 0\\ After\quad mole\quad \quad 1-\alpha \quad \quad  \alpha \quad\quad  \alpha \\ decomposition$

Total mole$=1-\alpha+\alpha+\alpha\\=1+\alpha$

Total pressure$=P$

Partial pressure of $PCl _5=P(\cfrac{1-\alpha}{1+\alpha})$

PArtial pressure of $PCl _3=P(\cfrac{\alpha}{1+\alpha})$

Partial pressure of $PCl _2=P(\cfrac{\alpha}{1+\alpha})$

Then $K _p=\cfrac{(PCl _3)(Cl _2)}{(PCl _5)}\\ \quad=\cfrac{P(\cfrac{\alpha}{1+\alpha})P(\cfrac{\alpha}{1+\alpha})}{P(\cfrac{1-\alpha}{1+\alpha})}\\ \quad=\cfrac{P^2\alpha^2}{(1+\alpha)^2}\times\cfrac{(1+\alpha)}{P(1-\alpha)}\\K _p=\cfrac{P\alpha^2}{1-\alpha^2}$

now, $1-\alpha^2<<1$

so that $K _p=P\alpha^2\\ \alpha^2=\cfrac{K _p}{P}\\ \alpha=\sqrt{\cfrac{K _p}{P}}$

 

If pressure of ${CO} _{2}$ (real gas) in a container is given by $P=\cfrac { RT }{ 2V-b } -\cfrac { a }{ 4{ b }^{ 2 } } $, then mass of the gas in container is:

real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

  1. $11g$

  2. $22g$

  3. $33g$

  4. $44g$

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Correct Option: B
Explanation:

According to Van Der waal's equation for $n$ mole of real gas 


$\bigg( P +\dfrac{n^2 a}{V^2}\bigg)(V- nb)=nRT\implies P=\dfrac{nRT}{V-nb}-\dfrac{n^2a}{V^2}$

Given that Pressure of $CO _2$ gas in a contaner is given by:
$P= \dfrac{RT}{2V-b}-\dfrac{a}{4b^2}$

Compairing it with the standard Van der waal's equation we get :
$n=\dfrac12$

Therefore, Number of moles in a container , $n=\dfrac12$
Molar mass of $CO _2= 44\ gm$
Mass of gas in the container, $m= \dfrac12\times 44 =22 gm$


Complete the following:
$1$ quintal $=$ _________ kg
physics measurements and experimentation measuring distance of celestial bodies unconventional units of measurements units of mass

  1. $10$

  2. $100$

  3. $1000$

  4. $0.01$

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Correct Option: B
Explanation:

A quintal is a unit of mass in the metric system which is equal to $100$ kilograms.

Mass is a ....................... quantity.

physics measurement and measuring instrument measuring distance of celestial bodies unconventional units of measurements units of mass

  1. Scalar 

  2. Vector

  3. Tensor

  4. All

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Correct Option: A
Explanation:

Since the physical quantity mass has only magnitude but not direction, thus mass is a scalar quantity.

What is the value of $1  \ m $ in $\mathring{A}$?

physics measurement and measuring instrument measuring distance of celestial bodies unconventional units of measurements units of mass

  1. $10^{-10}$

  2. $10^{5}$

  3. $10^{7}$

  4. $10^{10}$

Show answer
Correct Option: D
Explanation:
$1 m = 10^{10} \mathring{A}$
or we can say 1 angstrom $=10^{-10} m$
The natural sciences and technology often uses angstrom to express sizes of atoms, molecules, microscopic biological structures, and lengths of chemical bonds, arrangement of atoms in crystals, wavelengths of electromagnetic radiation.

The number of fermi in $1$ meter is _____. 

physics measurement and measuring instrument measuring distance of celestial bodies unconventional units of measurements units of mass

  1. $10^{13}$

  2. $10^{14}$

  3. $10^{15}$

  4. $10^{16}$

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Correct Option: C
Explanation:

Since,  $1\ Fm={10}^{-15}m$


$\therefore$  $\cfrac{1}{{10}^{-15}}Fermi =1m$

${10}^{15}Fermi=1m$

The unit of atomic mass is

physics measurement and measuring instrument measuring distance of celestial bodies unconventional units of measurements units of mass

  1. mu

  2. kg

  3. amu

  4. g

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Correct Option: C
Explanation:

Atomic mass is the mass of an atom. An atomic mass unit (symbolized AMU or amu) is defined as precisely $\dfrac{1}{12}$ the mass of an atom of carbon-12.

Which of the following is smallest unit of distance ?

physics measurements and experimentation measuring distance of celestial bodies unconventional units of measurements units of mass

  1. Milimeter

  2. Angstrom

  3. Fermi

  4. Meter

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Correct Option: C
Explanation:

Out of these, meter is the largest.
$1 millimeter = 10^{-3} m$
$1 Angstrom = 10^{-10}m$
$1 Fermi = 10^{-15}m$
Thus Fermi is the smallest.