A spontaneous reaction is a term that is best describe to a type of reaction wherein it is started without even with the help of an outside force. In addition to that, this kind of reaction is commonly driven by the forces of enthalpy and entropy which are essential concepts to thermodynamics.
When lava reaches the surface of the Earth through volcanoes or through great fissures the rocks that are formed from the lava cooling and hardening are called extrusive igneous rocks. Some of the more common types of extrusive igneous rocks are lava rocks, cinders, pumice, obsidian , and volcanic ash and dust.
Ba(NO₃)₂ + Na₂SO₄ → BaSO₄ + NaNO₃
By Trial and error.
Ba(NO₃)₂ + Na₂SO₄ → BaSO₄ + 2NaNO₃
Check:
LHS RHS
Ba 1 1
N 2 2
S 1 1
O 3*2 + 4 = 10 4 + 2*3 = 10