To determine the concentration of 5 Baume HCl, we can use the following formula:

Concentration (%HCl) = (Baume degrees - 0.7676) / 0.9988

Given that the Baume degrees for 5 Baume HCl is 5, let's plug this value into the formula:

Concentration (%HCl) = (5 - 0.7676) / 0.9988

Concentration (%HCl) = 4.2324 / 0.9988

Concentration (%HCl) ≈ 4.246 %

Therefore, the concentration of 5 Baume HCl is approximately 4.246 % HCl.