1. Balanced Chemical Equation:

The balanced chemical equation for the reaction is:

H₂(g) + Br₂(g) → 2HBr(g)

2. Mole Ratio:

The equation shows that 1 mole of Br₂ reacts to produce 2 moles of HBr.

3. Moles of HBr Produced:

Since we have 1.25 moles of Br₂, and the mole ratio is 1:2, we'll produce twice as many moles of HBr:

1.25 moles Br₂ * (2 moles HBr / 1 mole Br₂) = 2.50 moles HBr

4. Molar Mass of HBr:

The molar mass of HBr is:

* 1.01 g/mol (H) + 79.90 g/mol (Br) = 80.91 g/mol

5. Mass of HBr:

To find the mass of HBr, multiply the moles of HBr by its molar mass:

2.50 moles HBr * 80.91 g/mol = 202.28 g HBr

Therefore, the mass of HBr gas produced is 202.28 grams.