The molar mass of Fe would be 55.8450.
Answer: D:wavelenght
Explanation: Students will understand that shorter wavelengths have higher frequency and energy.
Answer: Out of the given options bonds connecting atoms in reactants break, and bonds connecting atoms in products form are the changes which takes place when a chemical change occurs.
Explanation:
A change that leads to the change in chemical composition of a substance is called a chemical change.
For example, 
Here, bond between the reactant atoms nitrogen and hydrogen is broken down.
On the other hand, bond connecting the products that is
and
is formed.
Thus,, we can conclude that out of the given options bonds connecting atoms in reactants break, and bonds connecting atoms in products form are the changes which takes place when a chemical change occurs.
Answer : Density of any particular matter remains the same at any concentration at any weight.
Density does not varies with the concentration. The formula for density is mass / volume.
So if the mass changes the density will change accordingly, also if the volume changes the density will get changed.
because, of the above reasons density is referred as a characteristic property of matter.