When should a plastic volumetric flask be used instead of a more accurate glass flask? 1. when measuring acids 2. when measuring hazardous chemicals - the plastic flask is disposable 3. when perfoming trace analysis and the analyte may adsorb to a glass surface

3.

Explanation:when performing trace analyses and the analyte may adsorb to the glass.

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 !

indium, and thallium have three electrons i think