Question

How to find out molality , molarity , mole fraction and molar mass ???

# Don't spam class 9

@ Prabhudutt.....

Answer 1

Heya......
Here is ur answer.......
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✡✡MOLARITY .....
= Weight of solute×1000
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Moecular weight of sulote ×vol. of solution.
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✡✡MOLELITY........
== Weight of solute×1000
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Molecular weight of solute× weight of solvent in gram

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✡✡MOLE FRACTION........
== No. of moles of sulute or solvent
------------------------------------------------------
Total no. of moles of solution.
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✡✡MOLAR MASS.....
FOR EXAMPLE...... The molecular formula of glucose is C6H12O6.....
Its molar mass can be calculated is as follows......
12(6) +1(12) +16(6)
=72+12+96
=180 ==This is the molar mass of glucose.
........
Now..... by taking atomic mass u can find molar mass of any molecule.
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HOPE THIS WILL HELP U

Answer 2

hi,


molality: it is the amount of solute present in 1 kg of the solute.

molality = number of moles of solute ÷ kg of solute.

eg: 15g of urea is dissolved in 200g of H2O. calculate the molality..

ans: ( the mass is given so you must convert it into moles by dividing given mass by molecular mass of the substance)

number of moles in NH2CONH2 (urea) =15 ( given mass) ÷ 60 ( molecular mass )
= 0.25 mol

molality = 0.25 (no. of moles) ÷ 0.2(kg of solvent) (convert 200g to kg = 0.2 kg)

=1.25m ( small letter m denotes molality )

so the molality is 1.25m

molarity : Amount of substance present in 1 dm cube or litres of the solution.

molarity = no. of moles of solute ÷ volume of solution in litres

here, first you have to find the number of moles in sol. then find the volume of sol. then divide them.

eg : calculate the molarity of the sol. prepared by dissolving 9.8 mol of solid NaOH with H2O to make sol. of 3.62 L

ans:

M = 9.8 (moles) ÷ 3.62(volume in litres)
= 2.7 M

so, the molarity is equal to 2.7 M ( M denotes molarity)

mole fraction:
i have added a picture related to this above....

molar mass: it is defined as the mass of the one mole of any substance that is element or compound.

eg: molar mass of Na = 23 g ( atomic mass)

molar mass of O2 means ( 16 x 2) = 32 ( atomic mass x 2)


hope it helps.......