$7/$
$nO2=2,24/22,4=0,1mol$
Ta có:
$2KMnO4→K2MnO4+MnO2+O2$
Theo pt:
$n_{KMnO4}=2n_{O2}=2.0,1=0,2mol$
$⇒m_{KMnO4}=0,2.158=31,6g$
$9/$
$a/$
$n_{O2}=6,4/32=0,2mol$
$C+O2\overset{t^o}{\rightarrow}CO2
Theo pt:
$n_{CO2}=n_{O2}=0,2mol$
$⇒m_{CO2}=0,2.44=8,8g$
$b/$
$nC=6/12=0,5mol$
$nO2=20/32=0,625mol$
$PTHH:$ $C + O2→CO2$
theo pt: $1mol$ $1 mol$
theo đbài: $0,5mol$ $0,625mol$
⇒Sau phản ứng O2 dư
Theo pt:
$n_{CO2}=n_{C}=0,5mol$
$⇒m_{CO2}=0,5.44=22g$