Problem: Determine the volume in mL of 0.3 M HI(aq) needed to reach the half-equivalence (stoichiometric) point in the titration of 41 mL of 0.47 M (CH3)2NH(aq)(aq).  The Kb of dimethylamine is 5.4 x 10-4.

We are asked to determine the volume in mL of 0.3 M HI(aq) needed to reach the half-equivalence (stoichiometric) point in the titration of 41 mL of 0.47 M (CH₃)₂NH(aq).

At the half-equivalence point, half of the moles of (CH₃)₂NH_(aq) will be consumed.

We'll go through the following steps to solve the problem

Step 1. Calculate the moles of  (CH₃)₂NH_(aq) 

Step 2. Calculate half of the moles of (CH₃)₂NH_(aq) 

Step 3. Calculate the volume of 0.3 M needed for half of the moles of (CH₃)₂NH_(aq) 

Step 1. Calculate the moles of  (CH₃)₂NH_(aq) 

recall: 

$\boxed{\mathbf{Molarity}\mathbf{ }\mathbf{=}\mathbf{ }\frac{\mathbf{moles}\mathbf{ }\mathbf{solute}}{\mathbf{L}\mathbf{ }\mathbf{solution}}}$