Question

rusting of iron is chemical change but according to law of conservation of mass it should not change its mass after chemical reaction....here iron is changing how?​

Answer 1

Answer:

Its correct that mass remains constant. But here in the chemical change, iron reacts with the atmospheric oxygen. Here's the equation for it:

                      4Fe+ 3$O_{2}$ → 2$Fe_{2}$$O_{3}$

Hence, here oxygen is added to iron, which increases its mass without violating law of conservation of mass.

Furthermore, here

Mass of iron=56 X4=224

Mass of oxygen=3 X 16 X2=96amu

Total LHS mass=320amu

Mass of 2$Fe_{2}$$O_{3}$=2 ( 56 X2 +16 X 3)=320amu=RHS

Mass of LHS = Mass of RHS