Which of the following is a decomposition reaction?

BaO + H2O → Ba(OH)2
CH4 + O2 → CO2 + H2O
CaO + CO2 → CaCO3
PbCO3 → PbO + CO2

Calculate the mass of carbon in 97.0 g of sucrose c12h22o11

Answer asap need it by wednesday morning calculate the ph of 0.02m hcl best answer will be brainliest

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!