An iron ore sample contains plus other impurities. A 729-g sample of impure iron ore is heated with excess carbon, producing 277 g of pure iron by the following reaction: What is the mass percent of in the impure iron ore sample?

Explanation:

m(total) = 729 g

m(pure) = 277 g

Mass of impure iron ore sample:

W(impure) - mass percent

W(impure) = m(total) - m(pure) / m(total) = 729 g - 277 g / 729 g

= 0,62 ⇒ 62%

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e