Question

How much heat should be transferred when 20.1 g of hydrogen bromide is formed during the reaction of hydrogen gas with liquid bromine?

Answer 1

9.1 KJ

Step-by-step explanation:

We must first put down the reaction equation;

H2(g) + Br2(g) ----> 2HBr(g)

Secondly we find the number of moles of HBr involved;

number of moles of HBr= mass of HBr/ molar mass of HBr

But molar mass of HBr= 80.91 g/mol

Given mass of HBr as given in the question= 20.1g

Hence;

Number of moles of HBr= 20.1 g/80.91g

Number of moles of HBr= 0.25 moles of HBr

Lastly we calculate the heat transferred from the number of moles involved;

If 2 moles of HBr has a heat of formation of 72.80KJ

Then 0.25 moles of HBr will have a heat of formation of 0.25× 72.80/2= 9.1 KJ

Then; 20.1 g of HBr will have a heat of formation of 9.1 KJ