Molality Problems (Need ASAP!) Thanks :)

1. What is the molality of a solution in which 0.135 moles of CO2 is dissolved in 490mL of water? (1kg of water = 1L of water)

2. What is the molality of a solution in which 23g of NaCl are dissolved in 250g of water?

3. How many moles of HC1 are needed to prepare a 3m (3molal) solution with 1.5Kg of water?

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"

the answer is 75.0%.