The concentration of the HBr would be 0.09 M
<h3>What are stoichiometric problems?</h3>
First, let us look at the equation of the reaction:
The mole ratio of HBr to NaOH is 1:1.
Mole of 15 mL, 0.30 M NaOH = 0.30 x 15/1000 = 0.0045 moles
Equivalent mole of HBr - 0.0045 moles
Molarity of HBr = mole/volume = 0.0045/50/1000 = 0.09 M
More on stoichiometric problems can be found here: brainly.com/question/15047541
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