[Mitoca]

Hi, I am in a Chem 122 course right now and I've been doing some problems out of my textbook.  Some of my answers aren't matching up.  But I think I'm doing them completely right.  I was just wondering if someone could double check the problems and tell me if the textbook is wrong or if I am just stupid.

Thanks.


1. A 0.944 M solution of glucose, C6 H12 O6, in water has a density of 1.0624 g/mL at 20 degrees Celcius.  What is the molality of this solution?

The text answer is given as 1.06m.  I don't remember my answer but I think it was between 1.6-2.0 molality.


2. The density of a 16.0 mass% solution of sulfuric acid in water is 1.1094 g/mL at 25 degress Celcius.  What is the molarity of the solution?

Text answer is given as 1.81M.  I got 1.66M.

[Padfoot]

1.
Molarity=0.944molL^-1
          =0.944*M_glucose=169.92gL^-1
Density=1.0624gmL^-1=1062.4gL^-1
Density of solvent= 1062.4-169.92=892.48gL^-1

Using this value and Molarity there is:
0.944mol glucose per 892.48g which equates to a molality of 1.057

2.
Density=1.1094gmL^-1
Density of solute=1.1094*0.16=0.1775gm^L-1=177.5gL-1
(using your mass%)
Molarity= 177.5/M_H2SO4=1.81