The rusting of iron is represented by the equation 4Fe + 3O2 --> 2Fe2O3. If you have a 3.5-mol sample of iron, how many grams of O2 are needed to rust the iron completely? 34.9 g
84.0 g
16.5 g
48.6 g

84.0 g

Balanced equation: 4Fe + 3O2 --> 2Fe2O3

Find moles of oxygen:

Find mass of O2

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g