Dozen = 12,
ii. 1 score = 20
iii. 1 ream = 500
iv. 1 gross = 1.44
Answer:
The first 50 elements along with their valences are given below :
1. Hydrogen = 1
2. Helium = 0
3. Lithium = 1
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
37. Rubidium = 1
38. Strontium = 2
39. Yttrium = 3
40. Zirconium = 4
41. Niobium = 3
42. Molybdenum = 3
43. Technetium = 7
44. Ruthenium = 4
45. Rhodium = 3
46. Palladium = 4
47. Sliver = 1
48. Cadmium = 2
49. Indium = 3
50. Tin = 4
<u>Note</u> :
An element like Iron, copper can have more than one valencies.
Each correspond to a principal energy level
Answer: 6.64 moles of carbon.
Explanation:
Given data:
Number of moles of C = ?
Number of moles of CCl₂F₂ = 6.64 mol
Solution:
In one mole of CCl₂F₂ there is one mole of carbon two moles of chlorine and two moles of fluorine are present.
In 6.6 moles of CCl₂F₂ :
Moles of carbon = 6.64 × 1 = 6.64 moles of carbon.
Moles of chlorine = 6.64× 2 = 13.28 moles of chlorine
Moles of fluorine = 6.64× 2 = 13.28 moles of fluorine
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