2. i believe that the answer is stoichiometry but im not sure of this. stoichiometry is the process of what i described in question 1. just with the addition of converting mols to mass if you know the average molar mass.
3. the answer is b. that is the only one that does not involve using the mole ratio of a formula to convert between reactants and products to find a quantity of either a reactant or product.
4. use the same process that i described in number 1. X mol of H2 *(1 mol N2)/(3 mol H2)
5. again use the same process as explained in 1 and 4
6. use the same methods again as before to find the mol of sulfur trioxide. then you need to look at a periodic table to find the molar mass of sulfur trioxide. you can then find the mass using the equation m =n*M
where m is mass
M is molar mass
and n is mols
7. this is the same as question 6 except you are given a mass at the start. you can alter the equation i gave you in #6 to convert to mols, use the process described in #1 to find the mols of the desired chemical, then convert back to mass
8. limiting reactant. the limiting reactant is the reactant that is completely used up and the excess is the reactant that is not. hence the name excess, since there will be some left over. this can be seen if you mix a cup of hot chocolate and put to much mix in. some of it doesnt dissolve. the mix is in excess and there is some that will not react, or in this case dissolve.
9. available about of each reaction. its a slightly more complicated process so im not gonna explain it because it seems you do not need to know this yet.
10. ok so it says excess water. this just means that the Mg2Si completely reacts. so you can just use the same process as #7. convert to mols, find mols of desired chemical, then convert back to mass.
sorry if i got anything wrong
good luck.