The student titrated a solution containing 0.0045 moles of sodium hydroxide with 0.15 mol/dm³ hydrochloric acid.
The equation for the reaction is:
NaOH + HCl → NaCl + H₂O
Calculate the volume of hydrochloric acid in cm³ needed in the titration.

This is a titration calculation. **Step 1: Determine the moles of HCl needed.** The balanced chemical equation is NaOH + HCl → NaCl + H₂O. The stoichiometric ratio between NaOH and HCl is 1:1. This means that 1 mole of NaOH reacts with 1 mole of HCl. Therefore, the number of moles of HCl needed is equal to the number of moles of NaOH. Moles of HCl = Moles of NaOH = 0.0045 mol. **Step 2: Calculate the volume of HCl.** We know the concentration of HCl is 0.15 mol/dm³ and we need 0.0045 moles of it. The formula is: Concentration = Moles / Volume Rearranging for Volume: Volume = Moles / Concentration Volume (in dm³) = 0.0045 mol / 0.15 mol/dm³ Volume = 0.03 dm³ **Step 3: Convert the volume to cm³.** To convert from dm³ to cm³, we multiply by 1000. Volume (in cm³) = 0.03 dm³ × 1000 cm³/dm³ Volume = 30 cm³