Answer:
The number that should be placed before F₂ is 2
Explanation:
For a chemical reaction to be balanced we need to have the same amount of mass in the reactants and in the products because by the<em> law of conservation of mass</em>, mass cannot be created or destroyed.
We can acomplish this by having the same amount of atoms of each element in the reactant side that in the product side.
For example:
C₃H₈ + 5O₂ → 3CO₂ + 4H₂0
In this case in the reactants side we have 3 C, 8 H and 10 O, so we have the same amount in the product side, so the equation is balanced.
In the equation Xe + F₂ → XeF₄ we have 1 Xe in each side, 2 F in the reactant side and 4 F in the product side, so we multiply the 2 F in reactan side to balance the equation.
Xe + 2Fe₂ → XeF₄