Question

The flask contains 10.0 mL of HCl and a few drops of phenolphthalein indicator. The buret contains 0.160 M NaOH . It requires 11.9 mL of the NaOH solution to reach the end point of the titration. A buret filled with a titrant is held above a graduated cylinder containing an analyte solution. What is the initial concentration of HCl

Answer 1

The initial concentration of HCl was 0.1904 M

Step-by-step explanation:

Step 1: Data given

Volume of HCl solution = 10.0 mL = 0.010 L

Volume of a NaOH solution = 11.9 mL = 0.0119 L

Molarity of NaOH solution = 0.160 M

Step 2: The balanced equation

HCl + NaOH → NaCl + H2O

Step 3: Calculate the concentration of HCl

C1*V1 = C2*V2

⇒with C1 = the concentration HCl = TO BE DETERMINED

⇒with V1 = the volume of HCl = 0.010 L

⇒with C2 = the concentration of NaOH = 0.160 M

⇒with V2 = the volume of NaOH = 0.0119 L

C1 * 0.010 L = 0.160 M * 0.0119 L

C1 = (0.160 M * 0.0119 L) / 0.010 L

C1 = 0.1904 M

The initial concentration of HCl was 0.1904 M

Answer 2

0.190 M

Step-by-step explanation:

Let's consider the neutralization reaction between HCl and NaOH.

HCl + NaOH = NaCl + H2O

11.9 mL of 0.160 M NaOH were used. The reacting moles of NaOH were:

0.0119 L × 0.160 mol/L = 1.90 × 10⁻³ mol

The molar ratio of HCl to NaOH is 1:1. The reacting moles of HCl are 1.90 × 10⁻³ moles.

1.90 × 10⁻³ moles of HCl are in 10.0 mL of solution. The molarity of HCl is:

M = 1.90 × 10⁻³ mol / 10.0 × 10⁻³ L = 0.190 M