Choose the best answer to complete each sentence: You______put the knife in your mouth - it’s very dangerous.

A. have to

B. don't have to

C. must

D. mustn't

247kg + 23kg = … kg

A/ 250

B/ 260

C/ 270

D/ 280

nO2 = 6,72 / 22,4 = 0,3 ( mol )

PTHH:

PT : 2H2 + O2 ----> 2H2O

TB : 0,6 : 0,3 : 0,6 ( mol )

m H2O = 0,6 * 18 = 10,8 ( g )

nO2 = 4,48 / 22,4 = 0,2 ( mol )

mO2 = 0,2 * 32 = 6,4 ( g )

PTHH:

3Fe + 2O2 ---> Fe3O4

ADĐLTBTKL:

mFe + mO2 = mFe3O4

<=> 20 + 6,4 = mFe3O4

<=> mFe3O4 = 26,4 ( g )