Which two equations represent double-replacement reactions? A. BaCl2 + Na2SO4 + 2NaCl + BaSO4
B. Ca + MgS - CaS + Mg
O C. HCI + KOH
KCI + H20
I D. 2C2H6 + 702 - 4CO2 + 6H20

Atoms seldom exist as independent particles in nature a) as single particles, most atoms have low potential energy b) their electronegativity is much lower when they combine with other atoms c) atoms are more stable when they combine with other atoms d) neutral particles are rare