mCuCO₃ = ?
p = 90%
Cu + 1/2O₂ ⇒ CuO
64g Cu..........................80g CuO
256g Cu.........................x = 320g CuO
CuCO₃ (t°C) ⇒ CuO + CO₂↑
124g CuCO₃..........................80g CuO
xg...........................................320g CuO
x = 124×320/80 = 496g CuCO₃ pur
p = m pur/m impur × 100 ⇒ m impur = 49600/90 = 551,1g CuCO₃