Calculate the molar mass of a gaseous substance if 0.125 g of the gas occupies 93.3 mL at STP. 30.2 g/mol
30.4g/mol
30.6 g/mol
30.0 g/mol
None of the above

30.0g/mol

Explanation:

Step 1: Given data

Step 2: Calculate the moles of the gas

We will use the ideal gas equation.

Step 3: Calculate the molar mass of the gas

4.16 × 10⁻³ moles correspond to a mass of 0.125 g. The molar mass of the gas is:

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

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