Question

A student performs a titration on 25.0 mL of 0.500M HCL(aq) which is placed in an Erlenmeyer flask. Two drops of indicator are added to the flask. An unknown concentration of NaOH(aq) is added to the buret the initial reading is 5.00 mL. The NaOH is added dropwise until the HCL solution is observed to be pink. The NaOH buret reading a t this point is 24.64mL. Please calculate the concentraion of the unknown NaOH Base

Answer 1

Answer:

The unknown NaOH base has a concentration of 0.636M

Explanation:

Step 1: the balanced equation

NaOH + HCl → NaCl + H2O

This means for 1 mole of NaOH consumed there is 1 mole of HCl needed to produce 1 mole of NaCl and 1 mole of H2O

Step 2: Calculate moles of HCl used

Number of moles = Concentration *  volume =  0.5M * 25*10^-3 L =0.0125 moles

Step 3: Calculate moles of NaOH

Since the mole ratio for HCl and NaOH is 1:1 this means we have 0.0125 moles of NaOH for 0.0125 moles of HCl

Step 4: Calculate Concentration of  the unknown NaOH base

Concentration = Number of moles / Volume

Volume of NaOH = 24.64-5 =19.64 mL = 0.01964 L

Concentration = 0.0125/0.01964 = 0.636 M

The unknown NaOH base has a concentration of 0.636M