Question

Elemental S reacts with O2 to form SO3 according to the reaction 2S+3O2→2SO3 Part A: How many O2 molecules are needed to react with 6.67 g of S? Express your answer numerically in units of molecules.

Part B: What is the theoretical yield of SO3 produced by the quantities described in Part A?
Express your answer numerically in grams.

Answer 1

Look at the stoichiometry...`S(s) + 3/2O_2(g) rarr SO_3(g)`

Explanation:

The stoichiometric coefficients are in terms of moles, and certainly this REPRESENTS a numerical quantity....i.e. where `N_A="Avogadro's number"=6.022xx10^23*mol^-1`.

With respect to sulfur we got a molar quantity of...

`(6.67*g)/(32.0*g*mol^-1)=0.208*mol`

And therefore CLEARLY we need `0.208*molxx3/2=0.313*mol` OF OXYGEN MOLECULES for stoichiometric equivalence.

`0.208*molxx3/2xx6.022xx10^23*mol^-1=1.88xx10^23*"oxygen molecules."`

And we use the mole here precisely as would the `"dozen"`, or the `"gross"`, as we would any other collective number...

And the mass of this quantity of oxygen is...?