You have a student who wiped the iodine with a tissue paper and the tissue paper turned purple. What does this color change in the tissue paper indicates? Please help me with this question

Nitric acid can be formed in two steps from the atmospheric gases nitrogen and oxygen, plus hydrogen prepared by reforming natural gas. in the first step, nitrogen and hydrogen react to form ammonia: (g) (g) (g) in the second step, ammonia and oxygen react to form nitric acid and water: (g) (g) (g) (g) calculate the net change in enthalpy for the formation of one mole of nitric acid from nitrogen, hydrogen and oxygen from these reactions. round your answer to the nearest .

Which of the following is a physical change? a. burning a piece of wood b. sawing a piece of wood in half c. rust forming on an iron fence d. a copper roof changing color from orange to green

Determine the length of the object shown. 97.8 mm 97.80 mm 97 mm 98 mm