A. The correctly balanced equation is that in which the number of atoms of a certain element at the left-hand side is similar to that in the right hand side or the reactant side and product side, respectively. From the given equation, the answer would be,
C. Cl2 + 2NaI --> 2NaCl + I2
B. In the given chemical reaction above, heat is emitted such that it appears in the product side of the equation. Hence, this is an example of a combustion reaction.
C. Similar with the reasoning in letter A, the answer to this item is,
B. 2H2 + O2 --> 2H2O
I'm guessing that this is a problem to find the weight of a 90kg mass on a planet where the acceleration of gravity is 4 m/s^2. (Much less gravity than Earth, a little more than Mars.)
Just do the multiplication, and you get
360 Newtons.
