Arrange the steps in order to describe what happens to a gas when it cools. the a particles of gas move slower.
b the gas changes to a liquid.
c the gas loses thermal energy.
d the space between the gas particles decreases.

The following steps occur sequentially when a gas cools down and become liquid.

1. Particles of gas move slower

2.The gas loses thermal energy.

3.The spaces between the gas particles decreases.

4. The gas changes to liquid.

The particles of gases are typically far apart and they move about randomly colliding with one another and with the wall of the container in which the gas is enclosed. When a gas is been cool down, the particles of the gas will lose kinetic energy and their movement will become slower, thus, they will lose thermal energy and the spaces between them will become reduced. As the cooling continues, the gas will eventually change to liquid.

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

it means there are 3 atoms of oxygen