Hydrogen gas and bromine gas react to form hydrogen bromide gas. How much heat (kJ) is released when 155 grams of HBr is formed in this reaction? ΔH° = - 72 kJ.

-37.63KJ

Explanation:

First, we write an equation of reaction:

H + Br - --> HBr

Now we are told that 155g of HBr is formed. We can calculate the number of moles of HBr formed as follows:

We simply divide the mass of the HBr formed by the molar mass of HBr. The molar mass of HBr is 81g/mol

The number of moles of HBr formed is thus 81/155 = 0.52 moles

The amount of heat released is thus 0.52 * (-72) = - 37.63KJ