What new characteristic did john dalton add to the model of the atom? (a) an atom is a round, solid mass.(b) an atom has a massive, positive center. (c)an atom is made up of smaller particles.(d) an atom can join with other kinds of atoms.

The right answer is D.

John Dalton is a British chemist and physicist who developed the atomic theory on which modern physical science was based.

The atom is, for chemists, the fundamental constituent of matter. The term comes from elsewhere a Greek word that means "indivisible", although it is known for a long time that this element is not.

The atom may be associated with other atoms, similar or different, to form a molecule (two oxygen atoms to form O2, or two hydrogen atoms with an oxygen atom to form H2O)

Basically he explained the principle of what is a molecule. He was wrong thinking that atoms are indivisible particles.

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g

i can ! i just need to know what the paragraph is! : p