The answer to your question is dependent variable.
On the basis of the given unbalanced equation, that is:
HBr (aq) + 2NaOH (aq) → 2NaBr (s) + H2O (l)
On the right side of the equation, there are 2 atoms of sodium (Na), 2 atoms of bromine (Br), 2 atoms of hydrogen (H), and 1 atom of oxygen (O₂).
After balancing the equation correctly we get:
HBr (aq) + NaOH (aq) → NaBr (s) + H2O (l)
On the right side, one atom of Na, 1 atom of Br, 1 atom of H and one atom of O₂.
Correct answer: "A. Energy from an outside source is continuously being added."
An endothermic reaction is a reaction that is characterised by the system absorbing energy from its surroundings. That energy is usually in heat form. For example, when mixing water<span> with potassium chloride, this reaction will absorb heat and the container will feel cold - endothermic reaction.</span>
