mrắn (sau khi nung) = \(\dfrac{300.78}{100}=234\left(g\right)\)
=> mCO2 = 300 - 234 = 66 (g)
=> \(n_{CO_2}=\dfrac{66}{44}=1,5\left(mol\right)\)
mCaCO3(bđ) = 300.80% = 240 (g)
PTHH: CaCO3 --to--> CaO + CO2
1,5<-----------------1,5
=> \(H\%=\dfrac{1,5.100}{240}.100\%=62,5\%\)