Answer :
The heat absorbed when bromine reacts with hydrogen is calculated using stoichiometry and bond energies. The masses of reactants are first converted to moles, the limiting reactant is determined, and then the total energy change is calculated. The process is exothermic, meaning heat is released.
To calculate how much heat will be absorbed when 38.2 g of bromine reacts with 12.4 g of hydrogen, you first need to understand the thermochemical equation associated with the reaction. The reaction given is: H₂(g) + Br2(g)
ightarrow 2HBr (g), and it involves the breaking and forming of chemical bonds. According to the given data, breaking an H₂ bond requires 436 kJ/mol, and breaking a Br₂ bond requires 193 kJ/mol. Forming two H-Br bonds releases 732 kJ/mol.
First, we convert the mass of bromine and hydrogen to moles using their molar masses. Bromine (Br₂) has a molar mass of approximately 159.8 g/mol, and hydrogen (H₂) has a molar mass of approximately 2.02 g/mol. Next, we apply the stoichiometry of the reaction to find the limiting reactant. After determining the number of moles of HBr that can be produced, we calculate the total energy change by adding the energy required to break the reactant bonds and subtracting the energy released by forming the product bonds.
The reaction is exothermic, as more energy is released than is absorbed, so the heat absorbed from the surroundings will be negative, indicating an exothermic process.