To calculate avogadro's number from the measured density of copper shot, what additional information is not needed? the molar mass of copper the atomic number of copper the length of the edge of the unit cell of copper the number of copper atoms occupying one unit cell of copper

Answer is Atomic Number of Cu.

Explanation: For a unit cell, density can be written as

For a unit cell, Mass will be

where Z= Number of atoms

m = Mass of an atom

Mass of an atom can be calculated by,

Volume of a unit cell =

where a = edge length

Now, putting Mass and Volume of an atom in density, the equation becomes

For the calculation of Avagadro's number,

we can see from the equation, we need

1. Molar mass of atom

2. Density of unit cell

3. Edge length of the unit cell

4. Number of atoms occupying one unit cell.

Hence, for the above question there is no need for the Atomic Number of atom.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !