Rusting of iron first increases then decreases - Science & Technology
Q. Rusting of iron ______________- Published on 10 Jun 15a. Decreases the weight
b. Increases the weight
c. Do not cause any change
d. First increases then decreases
ANSWER: First increases then decreases
When iron or any other metal oxidizes, oxygen from the air combines with the iron to make iron oxide or rust. So the first part of the answer is that the weight of the bar increases, due to the increased weight of oxygen which has combined with the iron. But the nature of the oxide that is formed. Iron oxide is non-adherent; either the volume of the oxide is greater or less than the volume of iron it replaced. So over time the rust will fall off of the bar. So if you look at something which has rusted for a long time (like my 75 Chevy pickup truck), the ground surrounding the iron part is coated with a layer of rust which has blown or washed off the iron part. So, over time, the weight of the iron bar will tend to decrease, due to factors related more to erosion than to chemistry.
