A sample of hydrogen has an initial temperature of 122.0 °F. When the temperature is lowered to -23.0 °F, the volume of hydrogen becomes 212 cm3. What was the initial volume of the hydrogen?

The initial volume of gas was

Explanation:

Charles's Law: This law states that volume is directly proportional to temperature of the gas at constant pressure and number of moles.

    (At constant pressure and number of moles)

where,

= initial volume of gas   =?

= final volume of gas =  

= initial temperature of gas  =    

= final temperature of gas  =

Therefore, the initial volume of gas was

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