How many covalent bonds does carbon form if each of its unpaired electrons participate in one bond?

Four covalent bonds.

Covalent (or homopolar) bonds occur based on the use or sharing of electron pairs. Covalent bonds are formed between nonmetallic elements.

We have the electronic configuration of a carbon atom as follows:  

From this, we can see that the carbon atom has four unpaired electrons which are in the outer shell, called the valence electron.  

Carbon atoms with four electrons in the outer shell need four more electrons to reach a stable electron configuration such as a noble gas. Therefore, carbon atoms can form four covalent bonds with other non-metal atoms such as hydrogen, oxygen, nitrogen, sulfur, halogens, and even with carbon atoms themselves.

Recall that a carbon atom can form single, double, or triple bonds with other carbon atoms.

Keywords: how many, covalent bonds, carbon, each of its unpaired electrons, participate in one bond, valence, outer shell, orbit, stable, the electronic configuration, non-metal atoms

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

i do not get it   at all