## mayankdevnani 3 years ago Can someone help me out. **BECOME FAN** **GIVE MEDALS** Q-) Can someone tell me briefly account on MOLES.

1. mayankdevnani

@.Sam. @phi @cwrw238 @radar @sara12345 @sauravshakya @surdawi @hba

2. mayankdevnani

@myko @amriju @Agent_Sniffles @mahmit2012 @him1618 @timo86m

3. mayankdevnani

plz help me

4. sara12345

mole is just a counting number. like, dozen = 12, mole = some number

5. mayankdevnani

yaa then

6. mayankdevnani

like some examples

7. sara12345

thats the concept. to count small particles in relation to mass, we use moles in chemistry

8. sara12345

do u have any specific question

9. sara12345

il have to think of an example...

10. mayankdevnani

no but i don't understand the formula of mole

11. sara12345

forget about the formula. therez no formula. mole is not a theory. its just a number, so we use the number in conversions.

12. sara12345

u wud be okay with mole, if u are familiar with dimensional analysis

13. mayankdevnani

nope

14. mayankdevnani

n(mole)=atomic weight/molar mass

15. sara12345

ok do u knw below two things : 1) atomic mass 2) molar mass

16. mayankdevnani

yaa

17. sara12345

could u tell me what they are

18. mayankdevnani

atomic mass means the atomic mass (ma) is the mass of a specific isotope, most often expressed in unified atomic mass units

19. mayankdevnani

the molar mass M is a physical property. It is defined as the mass of a given substance

20. mayankdevnani

right @sara12345

21. mayankdevnani

@sauravshakya

22. sara12345

partially correct.

23. mayankdevnani

so whats that

24. sara12345

in periodic table, the mass of each element is shown in unit amu, relative to carbon right ?

25. mayankdevnani

@sirm3d

26. mayankdevnani

right

27. sara12345

|dw:1351767227333:dw|

28. sara12345

N has a mass of 14 amu, Also, if u take one mole of N atoms, they would weigh 14 grams.

29. sara12345

thats the relation between 'mole and grams'

30. mayankdevnani

yaa

31. mayankdevnani

ok then

32. myko

mol is just a number 6.02214179×10^23

33. mayankdevnani

ok

34. amriju

u need to know whats a mole rite....well...in a part of chemistry called physical chemistry...u need to calculate mass volume etc of chemical substances....for that....to measure the number of molecules atoms etc of the compound in a given sample...we use the term moles....it gives us the number of atoms or molecules..in the given amount of specimen....it accualy is 6.023* $10^{23}$ units....just as a dozen means 12 units...so one mole of money means...6.023*10^23 rupess...

35. sara12345

so u can use the ratio $$\frac{1 mol}{atomic\ mass}$$ in your conversions

36. sara12345

to converst between $$mol$$ and $$grams$$

37. mayankdevnani

what is the formula of mole

38. sirm3d

a mole describes a fixed number of similar atoms or molecules a dozen means 12, a mole of nitrogen gas means 6.022x10^23 molecules of nitrogen gas

39. mayankdevnani

yaa i know but what's the formula of mole

40. sirm3d

1 mole = 6.022x10^23

41. amriju

now the mole is very special....since all that atomic weight u see is the weight of one mole of an atom in grams....same for moleclar wt.....also....for any gas..one mole of the gas occupies a volume of 22.4 litres at STP....so now u know that moles=Mass of the given specimen/ mol or atomic masss ( accordingly if its a molecule or an atom that the specimen is made of)

42. mayankdevnani

no how can we derive it

43. mayankdevnani

yaa thats what i have

44. mayankdevnani

@amriju can you give me examples of mole

45. sara12345

lets work out the example/question u had asked before, whats that ?

46. amriju

lets say u have 200 grams of NaCl...can u find out the number of moles..?

47. sara12345

lets not go to the compound level in the starting itself

48. sara12345

lets take an example which involves element only

49. mayankdevnani

Na=23g and Cl=35.5g

50. amriju

correct.....so NaCl has a molecular mass of.?

51. sara12345

ok great u seem to be having some idea of things already :)

52. mayankdevnani

200/58.5 moles

53. amriju

yooooooooooo

54. mayankdevnani

approx.

55. mayankdevnani

another some dificult

56. amriju

now find the number of moles of sodium ions in it....

57. mayankdevnani

not so much difficult

58. amriju

59. mayankdevnani

23 of $Na^+$

60. mayankdevnani

right?

61. amriju

number of moles of Na+

62. mayankdevnani

23g of Na+

63. amriju

thats the weight of Na+...i want the numbr of moles of it

64. mayankdevnani

sorry.. i don't know

65. sara12345

did u get the question

66. sara12345

question is this : find number of moles of Na+ in 2000 grams of NaCl

67. mayankdevnani

how can you identify question @sara12345

68. sirm3d

the number of moles of Na+ is the same as the number of moles of NaCl, which is 2000/58.5 moles

69. amriju

ok....u found the number of moles of nacl...k?..lets hav another ques...find the number of Na+ ions in a dozen of NaCl molecules

70. rduncan16

did i barge in

71. amriju

72. mayankdevnani

yaa you can @rduncan16

73. mayankdevnani

wait....

74. mayankdevnani

i don't get answer @amriju help me!!!!

75. rduncan16

cuz i can give u the actuial formulia

76. mayankdevnani

yaa you can

77. amriju

how many Na+ atoms r there in 1 nacl molecule....nacl=na+ +cl-.....

78. mayankdevnani

so its 58.5g

79. mayankdevnani

@amriju @sara12345

80. mayankdevnani

@UnkleRhaukus

81. UnkleRhaukus

hmm, whats the question, something about a mole?

82. mayankdevnani

how many Na+ atoms r there in 1 nacl molecule

83. UnkleRhaukus

the NaCl molecule has one sodium atom and one chlorine atom only

84. mayankdevnani

yaa

85. mayankdevnani

then

86. UnkleRhaukus

one mole of NaCl has 6x10^23 molecules, so in one mole of NaCl there will be 6x10^23 sodiums and 6x10^23 chlorines

87. mayankdevnani

ok

88. UnkleRhaukus

easy ?

89. mayankdevnani

90. UnkleRhaukus

the H_2O molecule has two hydrogen atoms and one oxygen atom one mole of H_2O has 6x10^23 molecules, so in one mole of H_2O there will be 12x10^23 Hydrogens and 6x10^23 Oxygens

91. UnkleRhaukus

92. mayankdevnani

how many Na+ atoms r there in 1 nacl molecule

93. UnkleRhaukus

one

94. sara12345

friend, precicely this is the reason, i hinted u to take an example that contains only elements

95. sara12345

when we are studying the concept of mole, it makes no sense to deal with compounds.

96. sara12345

compounds wil come much later

97. UnkleRhaukus

?

98. mayankdevnani

ok

99. sara12345

this is the logical order we study things in chemistry : 1) atoms- models 2) compounds 3) reactions

100. sara12345

mol concept is very basic, we learn it along with atomic mass and molar mass, in first module, atoms-models

101. sara12345

once we get confident with atoms, mole conversions to grams and number of atoms, fully, we move to next module compounds.

102. mayankdevnani

sorry... meet tomorrow... thnx...for coming ....will be right back ...i tag you

103. sara12345

NaCl is an ionic compound, which will not make sense to u, when we r living in module 1

104. mayankdevnani

ok @UnkleRhaukus @sara12345 @amriju @thivitaa

105. UnkleRhaukus

What

106. sara12345

ok, mean while try to work this simple q : whats the mass of 2.35 moles of carbon ?

107. UnkleRhaukus

we know 12 g of carbon is a mole

108. sara12345

you could use that

109. sara12345

and another example : how many moles are in 100 grams of carbon ?

110. mayankdevnani

111. mayankdevnani

plz @amriju for practise

112. amriju

i cant help u here...bring me ques..i can help...but i cant really form tough ques...:(

113. mayankdevnani

114. mayankdevnani

@amriju

115. amriju

k....water was poured on sulphuric acid....making the temperature of the flask around 300 degrees and causing 25 percent of acid to vaporise...if the volume of the acid in gaseous state was x cc find 1) the number of moles of acid..2) total weight of the acid before water was poured

116. amriju

this is a pretty tough ques...

117. mayankdevnani

yaa well try this...isme kya bura hai

118. amriju

tumne charles nd boyles law kr liye ho..?