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Burka [1]
3 years ago
5

An exciton is: A charged particle made of electrons A charged particle made of holes A neutral particle made of an electron and

hole A photon in an excited state
Chemistry
1 answer:
Alex3 years ago
7 0

Answer:

A neutral particle made of an electron and hole

Explanation:

Exciton

It is the combination of an electron and a hole ( hole refers to the vacancy of an electron ) . And , as both the electron and the hole have the same charge but the polarity is opposite , the combination will lead to a neutral compound , i.e. ,  Exciton have no charge and so neutral .

It is free to move in the nonmetallic crystal and since it charge less , it is difficult to detect it directly .

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Use the reaction 1₂(s) = 12(g), AH = 62.4 kJ/mol, AS = 0.145 kJ/(mol-K), for
Sati [7]

The Reaction is spontaneous when temperature is 430 K. Hence, Option (C) is correct.

<h3></h3><h3>What is Spontaneous reaction ?</h3>

Reactions are favorable when they result in a decrease in enthalpy and an increase in entropy of the system.

When both of these conditions are met, the reaction occurs naturally.

Spontaneous reaction is a reaction that favors the formation of products at the conditions under which the reaction is occurring.

According to Gibb's equation:

ΔG = ΔH - TΔS

ΔG = Gibbs free energy

ΔH = enthalpy change  = +62.4 kJ/mol

ΔS = entropy change  = +0.145 kJ/molK

T = temperature in Kelvin

  • ΔG  = +ve, reaction is non spontaneous
  • ΔG = -ve, reaction is spontaneous
  • ΔG   = 0, reaction is in equilibrium

ΔH - TΔS = 0 for reaction to be spontaneous

T = ΔH / ΔS

Here,

T = 500K

Thus the Reaction is spontaneous when temperature is 500 K.

Learn more about Gibbs free energy here ;

https://brainly.in/question/13372282

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3 0
2 years ago
What is the velocity of a electron whose wavelength is 100 pm?
Anni [7]

Answer:

v = 7.3 × 10⁶ m/s

Explanation:

Given data:

Velocity of electron = ?

Wavelength = 100 pm

Solution:

Formula:

λ = h/mv

λ = wavelength

h = planck's constant

m = mass

v = velocity

Now we will put the values in formula.

100 ×10⁻¹² m = 6.63 × 10⁻³⁴ j.s / 9.109 × 10⁻³¹ kg ×  v

v = 6.63 × 10⁻³⁴ kg.m²/s /  9.109 × 10⁻³¹ kg ×100 ×10⁻¹² m

v = 6.63 × 10⁻³⁴ m/s /910.9 × 10⁻⁴³

v = 0.0073  × 10⁹ m/s

v = 7.3 × 10⁶ m/s

5 0
3 years ago
How are models useful in describing how molecules are formed
Nady [450]

Answer:

The purpose of molecular modeling is to provide a three-dimensional image (either physical or software-based) that allows a chemist to better see the manner in which atoms and molecules can interact. These models can be used to interpret existing observations or to predict new chemical behavior.

Explanation:

It can describe shape and how they connect while forming the electrons.

6 0
3 years ago
!: (a) 20 cm: 80
RoseWind [281]

Answer:

THE LENGTH OF THE AIR COLUMN IS 9.5 CM

Explanation:

Taking the atmospheric pressure to be 760 mmHg;

When the capillary tube is held horizontally, the pressure of the tube is 760 mmHg

when the capillary tube is held vertically, the pressure increases by 4 cm = 40 mm

The new pressure of the tube is hence, 760 + 40 mmHg = 800 mmHg

Using the pressure forlmula;

P1 V1 = P2 V2

P1 A1 L1 = P2 A2 L2

where A1 and A2 is the area of the capillary tube and it is equal, it cancels out.

P1 l1 = P2 l2

l2 = P1 l1 / P2

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The length of the air in the tube is 9.5 cm.

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3 years ago
Match the following vocabulary words with the correct definitions.
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1- evaporation 2- transpiration 3-condensation 4- precipitation
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