PLEASE HELP ME WITH THIS BASIC QUESTION....
25g of a solute of molar mass 250g/molecular is dissolved in 100ml of water to form a. Solution whose density is 1.25 g/ml. The molality is? ( answer =0.8) please solve it.
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It is given tht 25 gm of solute of molar mass 250 is dissolved in 100ml of water
--> No.of moles of solute present in the solution is 25÷250 = 0.1 mole
And Since , density of the solution is 1.25 gm /ml
--> mass of 100 ml solvent i.e. water will be 100× 1.25 gm = 125 gm
Therefore molality (m ) = (0.1×1000 )÷(125) = 0.8.
--> No.of moles of solute present in the solution is 25÷250 = 0.1 mole
And Since , density of the solution is 1.25 gm /ml
--> mass of 100 ml solvent i.e. water will be 100× 1.25 gm = 125 gm
Therefore molality (m ) = (0.1×1000 )÷(125) = 0.8.
NavdeepDhingra:
Don't we consider mass of solvent and not solution? Plz reply fast
No we will consider only the mass of solvent here Because this is the case of molality . and the molality means the no.of moles of solute dissolved in one kg of the solvent .
Exactly what I am saying weight of solution is 125 and not weight of solvent as density of solution is given.
So answer provided in my book is wrong and it should be 1m.
so .. as per this the mass of the solvent to b considered is 125-25 =100 gm .. but it doesnot seems to suit this question.
It may be.
well i think it perfectly suits the question..
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if it is useful mark it as brainliest answer
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