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Nataliya [291]
3 years ago
11

An X-ray beam with λ = 157 pm incident on the surface of a crystal produced a maximum reflection at an angle of θ = 28.5 ∘. Assu

ming n=1, calculate the separation between layers of atoms in the crystal.
Chemistry
1 answer:
WARRIOR [948]3 years ago
8 0

Answer:

The separation between layers of atoms in the crystal is 164.52 pm.

Explanation:

Formula used

n \lambda = 2d\sin \theta (Bragg's law)

Where :

n = an order of reflection (integer)

\lambda = wavelength of the beam incident X-ray

d = spacing between the layer

θ = incident angle ( angle between ray and scatter plane)

We have :

λ = 157 pm

θ = 28.5°

n = 1

d = ?

1\times 157 pm= 2d\sin (28.5^o) (Bragg's law)

d=\frac{1\times 157 pm}{2\times \sin (28.5^o)}=164.52 pm

The separation between layers of atoms in the crystal is 164.52 pm.

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The work function for metallic potassium is 2.3 eV. Calculate the velocity in km/s for electrons ejected from a metallic potassi
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Answer:

932.44 km/s

Explanation:

Given that:

The work function of the magnesium = 2.3 eV

Energy in eV can be converted to energy in J as:

1 eV = 1.6022 × 10⁻¹⁹ J

So, work function = 2.3\times 1.6022\times 10^{-19}\ J=3.68506\times 10^{-19}\ J

Using the equation for photoelectric effect as:

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Also, E=\frac {h\times c}{\lambda}

Applying the equation as:

\frac {h\times c}{\lambda}=\psi _0+\frac {1}{2}\times m\times v^2

Where,  

h is Plank's constant having value 6.626\times 10^{-34}\ Js

c is the speed of light having value 3\times 10^8\ m/s

m is the mass of electron having value 9.11\times 10^{-31}\ kg

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\psi _0=Work\ function

v is the velocity of electron

Given, \lambda=260\ nm=260\times 10^{-9}\ m

Thus, applying values as:

\frac{6.626\times 10^{-34}\times 3\times 10^8}{260\times 10^{-9}}=3.68506\times 10^{-19}+\frac{1}{2}\times 9.11\times 10^{-31}\times v^2

3.68506\times \:10^{-19}+\frac{1}{2}\times \:9.11\times \:10^{-31}v^2=\frac{6.626\times \:10^{-34}\times \:3\times \:10^8}{260\times \:10^{-9}}

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\frac{1}{2}\times 9.11\times 10^{-31}\times v^2=3.96032462\times 10^{-19}

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Also, 1 m = 0.001 km

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Explanation:

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Hence, formula to calculate slope of the graph is as follows.

   The slope of graph = \frac{\text{difference in absrobance at two points}}{\text{difference in concentrations at those points}}

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Answer:

The first 50 elements along with their valences are given below :

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4. Beryllium = 2

5. Boron = 3

6. Carbon = 4

7. Nitrogen = 3

8. Oxygen = 2

9. Fluorine = 1

10. Neon = 0

11. Sodium = 1

12. Magnesium = 2

13. Aluminium = 3

14. Silicon = 4

15. Phosphorus = 3

16. Sulphur = 2

17. Chlorine = 1

18. Argon = 0

19. Potassium = 1

20. Calcium = 2

21. Scandiun = 3

22. Titanium = 3

23. Vanadium = 4

24. Chromium = 3

25. Manganese = 4

26. Iron = 2

27. Cobalt = 2

28. Nickel = 2

29. Copper = 2

30. Zinc = 2

31. Gallium = 3

32. Germanium = 4

33. Arsenic = 3

34. Selenium = 2

35. Bromine = 1

36. Krypton = 0

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38. Strontium = 2

39. Yttrium = 3

40. Zirconium = 4

41. Niobium = 3

42. Molybdenum = 3

43. Technetium = 7

44. Ruthenium = 4

45. Rhodium = 3

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48. Cadmium = 2

49. Indium = 3

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An element like Iron, copper can have more than one valencies.

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