What kind of intermolecular forces act between a hydrogen cyanide molecule and a potassium cation? If there is more than one type of intermolecular force that acts, be sure to list them all, with a comma between the name of each force.
(dipole, hydrogen-bonding, dispersion, ion-dipole)

ion-dipole

Explanation:

Let us remember that the potassium cation is an ion, a positive ion to be precise.

There is a dipole existing in the hydrogen cyanide molecule. The positive end of the dipole is on hydrogen while the negative end of the dipole is on the cyanide moiety.

The only possible interaction between the potassium cation and the hydrogen cyanide is an ion dipole interaction. The cation interacts with the cyanide moiety having a partial negative charge in the molecule.

"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"