Double Displacement Reaction Outcomes + Balancing?

Question

I cannot figure out the following questions:
MgCl2 + NaOH ==>
FeCl3 + NaOH ==>
Na2CO3 + HCI ==>
NH4Cl + NaOH ==>
I need to get their products and also balance them.

And I also need to know how to put the following two into decomposition reactions that lead to a formation of water and gas:
Na2CO3 + HCI ==>
NH4Cl + NaOH ==>


Thanks for all your help.
:)

Answer 1

MgCl2 + NaOH==> Mg(OH)2 + NaCl

why? because Mg has a charge of +2, so the "2" goes to OH because when you bond compounds, the charges are criss-crossed...by the way, OH is -1 so Mg has no subscript no...Na is +1 and so is Cl-1, so they are just NaCl because their charges are 1...not Na2Cl or NaCl2...just NaCl

in balancing equations, you just add a numerical coefficient before the compounds,, make sure that the number of each element in the reactant side, will equal to the number of elements in the product side...like reactant side=there are 2 Cl, so there must also be 2 Cl in the product side...

balanced equation for MgCl2 + NaOH==>MgOH2 + NaCl:

MgCl2 + 2NaOH==>Mg(OH)2 + 2NaCl

try to count the elements, they're equal...1 Mg, 2 Cl each, 2 Na each, and 2 OH

Answer 2

MgCl2 + 2NaOH -----> Mg(OH)2 + 2NaCl

The next one is very similar, with 3s all round.

Na2CO3 + 2HCl ---> 2NaCl + CO2 + H2O

NH4Cl + NaOH ---> NaCl + NH3 + H2O