#1
[tex]\\ \sf\longmapsto2 Ca+O_2\longrightarrow 2CaO[/tex]
Balanced
#2
[tex]\\ \sf\longmapsto N_2+3H_2\longrightarrow 2NH_3[/tex]
Balanced
#3
[tex]\\ \sf\longmapsto 2Cu_2O+C\longrightarrow 4Cu+CO_2[/tex]
Balanced
#4
[tex]\\ \sf\longmapsto H_2O_2\longrightarrow H_2O+O_2[/tex]
Already balanced
