1. Mg + CuSO4 —> MgSO4 + Cu
=> Single displacement reaction
2. 2HCI + Mg(OH)2 —> MgCI2 + H2O
=> Acid - base reaction
3.AgNO3 + NaCI —> AgCI + NaNO3
=> Double displacement reaction
They are hard solid with a crystal lattice structure... with high melting points
Your answer would be 250,000
C. Grams per Cubic Centimeter