A solution is prepared by dissolving 76.3 g NaI in 545 g of water. Determine the mole fraction of NaI if the final volume of the solution is 576 mL.

Mole fraction NaI → 0.016

Explanation:

Mass of solute: 76.3 g (NaI)

Mass of solvent: 545 g (H₂O)

Let's determine the moles of each:

Mol of solute → 76.3 g . 1 mol/ 149.89 g = 0.509 moles

Mol of solvent →  545 g . 1mol/ 18 g = 30.2 moles

To calculate the mole fraction → Moles of solute / Total moles

Total moles = 0.509 + 30.2 → 30.709

Mole fraction NaI = 0.509 / 30.709 = 0.016

"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"

your answer would be “dry”