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A solution is prepared by dissolving 171g of CdCl2 in enough water to make 250.0 mL...

A solution is prepared by dissolving 171g of CdCl₂ in enough water to make 250.0 mL of solution. If the density of the solution is 1.556 g/mL, calculate: Molarity of the solution, mole fraction of CdCl_2, and molality of the solution.

Expert Solution

Step 1, -

Calculate number of moles of CdCl2 dissolved in water to prepare 250ml solution

...........................................................................= Wt. of CdCl2 / Molecular mass of CdCl2 ...........................................................................= 171 / 183.41............................................

...........................................................................= 0.9323 moles............................................

.................. number of moles per litre of solution = ( 0.9323 x 1000) / 250...= 3.7292 moles

Step 2`, - Calculation of Molarity (M) of Cd Cl2 Soln.

Since, Molarity (M) = Number of moles per litre of solution

...........................= 3.7292 M

..........................or, = 3.73 M

Step 3 ,

Calculation fpr molality of CdCl2 solution :

.....................................Given density of solution = 1.556 gms / ml

weight of 1000 ml of solution = 1.556 x 1000 = 1556 gms.

Now 1556 gms of solution contains CdCl2 .......... = 3.73 moles

...............................................................................= 3.73 x 183.414

............................................................................... = 684.13 gms

hence , weight of water in one litre or 1000 gms of solution = (1556 - 684.13) gms

................................................................................................ = 871 .87 gms

So , 871.87 gms of water in solution contains the number of moles of CdCl2 = 3.73 moles

1000 gms ( or 1 Kg ) of water in solution.....................................= ( 3.73 x 1000 ) / 871. 87

........................................................................................................................... = 4.278 moles

....................................................................................................................or,... = 4.28 moles

Step -4 ,

Now, we know that molality of a solution = Number of moles of solute per Kg of solvent

therefore this represents the molality ( m) of prepared CdCl2 solution as ..........= 4.28 m

step 3 ,-

Calculation of mole fraction of CdCl2

Since mole fraction of solute = moles of solute / total of the (number of moles of solute + moles of solvent )

Therefore, mole fraction of CdCl2 = 4.28 / 4.28 + (1000/18 )

.....................................................= 0.0715

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queen_honey_blossom answered 2 years ago

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