Calculate Mass of Paradichlorobenzene for .05 Molal Solution

[babbagee]

Calculate the mass of paradichlorobenzene (M=147.01g/mol) that should be added to 20.00 ml of cyclohexane (d = .779g/ml) to make a .05 molal solution.

I did this problem but i don't know if i did it correctly.
first i found the mass of cyclohexane by using m=dv.

(.05moles solute/kg solvent)(15.58g)(1kg/1000g)(147.01g/mol) = .11g

does this seem correct. I am not sure.

Thanks.

 

[thunderfvck]

That's what I got...

 

[ravenprp]

The calculation you have done seems to be correct. To confirm, we can use the formula for molality (m) which is moles of solute (n) divided by mass of solvent (m) in kilograms.

m = n/m

Given that the molality (m) is 0.05 molal and the mass of solvent (m) is 20.00 ml of cyclohexane, we can rearrange the formula to solve for the mass of solute (n).

n = m x m

n = (0.05 molal) x (20.00 ml/1000g) x (0.779 g/ml) = 0.0779 g

This is very close to the value you have calculated, so your answer seems to be correct. Keep in mind that there may be slight variations due to rounding off of numbers.