Red phosphorus reacts with liquid bromine in an exothermic reaction: 2 P(s) + 3 Br₂(l) ► 2PBr₃(g)
ΔH° = -243.0 kJ
Calculate the enthalpy change when 2.63 g of red phosphorus reacts with 25.0 g of Br₂.

h let me think

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

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