A mixture a. Can always be separated using filtration
b. Contains substances that are not mixed in a specific ratio
c. Is made when two or more elements chemically combine with each other
d. All of the above

b. Contains substances that are not mixed in a specific ratio

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 !

some sources quote the lethal dose, for an average 170lbs opiate-naive individual is between 75 and 375 mg