Yes you are right .. X is undergoing a change from solid to gas at point E
The gram-formula mass means that the mass of one mole molecule. Then you just need to calculate the elements together. So the gram-formula mass of (NH4)3PO4 is equals to (14+4)*3+31+16*4= 149g/mol. So the answer is (c)
It is a moderate conductor of electricity, and in nature it is a dark indigo blue mineral. Density: 4.6g/cm^3. insoluble in water. melting point above 500 degrees C.
Density = Mass/Volume
d= 5 / 4.5
