Answer:
mNaCl = mNa + mCl
mNa = 20g
mCl = mCl2/2 = 30/2 = 15g
mNaCl= 20+15 = 35g
If the bonds are held together tightly, as an ionic bond or even a covalent bond, there will need to be a strong force to separate those bonds. This would by why their would be a high melting point. Another reason would be re-activity. <span />