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Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

The clouds float in the atmosphere because of their low.

  1. Pressure

  2. Velocity

  3. Temperature

  4. Density
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
As the rule of thumb, you can assume that the things with less density float on things with higher density. And water do have less density than air that's the reason clouds float in the atmosphere.
Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Sea water at frequency $\nu \  =\  4\  x\  { 10 }^{ 8 }$ Hz has permittivity $\varepsilon  \  \approx \  80\  { \varepsilon   } _{ 0 }$, permeability $\mu \  \approx \  { \mu  } _{ 0 }$ and resistivity $\rho \  =\  0.25\  \Omega m$. Imagine a parallel plate capacitor immersed in sea water and driven by an alternating voltage source V(t) = ${ V } _{ 0 }\  \sin { \  (2\pi \nu t) }$. The of amplitude of the displacement current density to the conduction current density is

  1. $\dfrac { 2 }{ 3 }$
  2. $\dfrac { 4 }{ 9 }$
  3. $\dfrac { 9 }{ 4 }$

  4. 2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Suppose distance between the parallel plates is $D$ and applied voltage $V _{(t)} = V _02\pi vt$.

thus electric field
$E = \dfrac{V _0}{d} \sin (2\pi vt)$
Now using Ohm's law 
$J _c = \dfrac{1}{\phi} \dfrac{V _0}{d}\sin (2\pi vt)$

$\dfrac{V _0}{\phi d}\sin  (2 \pi vt) = J _0^c \sin  2 \pi vt$

Here $J _0^c = \dfrac{V _0}{pd}$
Now the displacement current density is given as
$Jd = \in \dfrac{\delta E}{dt} =\dfrac{\in \delta}{dt}$    $\left[\dfrac{V _0}{dt} \sin (2\pi vt)\right]$

$= \dfrac{\in 2\pi v V _0}{d} \cos (2\pi vt)$

$\Rightarrow = J^d _0 \cos (2\pi vt)$

Where $J _0^d = \dfrac{2\pi V\in V _0}{d}$

$\Rightarrow \dfrac{J^d _0}{J^c _0} = \dfrac{2\pi v \in V _0}{d}. \dfrac{pd}{V _0} = 2\pi v \in \rho$

$= 2\pi \times 80\in _0v\times 0.25 = 4\pi \in _0v \times 10$ 

$= \dfrac{10v}{9\times 10^9} = \dfrac{4}{9}$

Multiple choice chemistry non-metals introduction to non-metals occurence of metals occurrence of metals and non metals

Which statement is false?

  1. Elements of VB group are transition elements

  2. Elements of VA group are all metalloids

  3. Elements of IA and IIA groups are metals

  4. Elements of IVA group are neither strongly electronegative nor strongly electropositive
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In element of $VA$ only arsenic and antimony are metalloids where as nitrogen and phosphorus are non metal. Bismuth and moscovium are metal.

Multiple choice chemistry non-metals introduction to non-metals occurence of metals occurrence of metals and non metals

Which of the following is the most reactive metal?

  1. Copper

  2. Gold

  3. Silver

  4. Francium
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Francium, right on the bottom of the group one of periodic table. As we know,size of the atoms increases as you go down a column and decreases as you go across the table. The larger the atom, the easier is to get rid of the valence electrons and easier to react with other atoms. Now if you look at the periodic table, francium has the largest radius therefore it is the most reactive element.

Multiple choice chemistry non-metals introduction to non-metals occurence of metals occurrence of metals and non metals

Nitrogen and germanium are:

  1. metal and non-metal respectively

  2. metal and metalloid respectively

  3. non-metal and metalloid respectively

  4. non-metal and metal respectively
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Hydrogen, oxygen, nitrogen etc. are non-metal and boron, silicon, germanium etc. are metalloids. On the basis of chemical and physical properties, elements are further classified into metals, non metals and metalloids.

Multiple choice chemistry non-metals introduction to non-metals occurence of metals occurrence of metals and non metals

Mark the correct statement.

  1. Some metals are found in earth's crust in the free state

  2. Metals at the bottom of activity series are least reactive

  3. Gold, silver can never be found in free state

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Some metals are found in earth's crust in the free state. Some are found in the form of their compounds. The metals at the bottom of activity series are least reactive.