Are the following equations balanced or unbalanced?

1. SnO2 + 2H2 → Sn + 2 H2O


2. 4NH3 + 5O2 → 4NO + 6H2O


3. 2B2Br6 + 5HNO3 2 B(NO3)3 + HBr



4. 2KNO3 + 1H2CO3 → 1K2CO3 + 2HNO3