Help, please. balance these equations by writing the proper coefficients in the blanks provided. 1. Mg + O2 --> MgO
2. P + O2 --> P2O5
3. S + O2 ---> SO2
4. Na + Cl --> NaCl
5. CaCO3 --> CaO + CO2

thank you :)

Before it was launched, a helium-filled balloon had a pressure of 201 kpa at a temperature of 27°c. at an altitude of 15,000 m, the pressure had decreased to 2.5 kpa and the temperature had dropped to -14 °c. the volume of the balloon increased to 59.3 m3. what is the original volume of the balloon? 13 m3 0.85 m3 0.077 m3 1.17 m3