In a chemical reaction, the reactants are substances that undergo the reaction, and the products are substances that are formed during the reaction. The table below shows the reactants and products of several different chemical reactions. Reactants Products Type of Reaction
4K + O2 2K2O + heat Exothermic
2H2O + heat 2H2 + O2 Endothermic
2CO + O2 2CO2 + heat Exothermic
CaCO3 + heat CaO + CO2 Endothermic

Based on the information given in the above table, the best definition of an endothermic reaction would be
A.
a reaction that absorbs heat.
B.
a reaction that has one product.
C.
a reaction that does not require heat.
D.
a reaction that releases heat.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

no, the red giant is the hottest with 2.00.000.000 degrees celsius. while the white dwarf only 25,000 degrees celsius.