Br2 + NaF —> Which best completes the chemical equation?

When Br2 and NaF are mixed, no reaction would occur since Br cannot replace F in NaF which gives NaBr + F₂ as products. Hence, Fluorine is more reactive than Bromine. Hence, Br can't replace F.  

Explanation:

When two reactants Br2 and NaF are mixed, no reaction takes place since Br cannot replace F in NaF. By seeing the periodic table, the positions of the halogens in the periodic table, bromine is located way below fluorine.Bromine will not have sufficient energy to replace fluorine and so it will not have energy which is sufficient to join because of low reactivity.  Among these fluorine represents the most reactive element among halogens.Some of you may think it is a single replacement reaction that gives NaBr + F₂ as products. But, according to the halogen reactivity, it decreases from top to down of the group. F is placed above Br. Hence, Fluorine is more reactive than Bromine. Hence, Br can't replace F.  

 

The heat flow would be from he counter to the ice cube, because the ice cube is colder than the counter and heat moves from high heat to low heat.