Question

10.00 mL sample of aqueous HCl requires 31.00 mL of 0.0900 M NaOH to reach the endpoint. What is the molar

concentration of HCl.

Answer 1

The molar concentration of the HCl solution is calculated using the titration data with NaOH. By determining the moles of NaOH used, we find it to be equal to the moles of HCl due to the 1:1 mole ratio. Dividing the moles of HCl by the volume of the acid gives us the molarity of the HCl solution, which is 0.279 M.

Step-by-step explanation:

Titration Calculation to Determine Molarity of HCl

To find the molar concentration of the hydrochloric acid (HCl) solution, we can use the titration data provided. The balanced chemical equation for the reaction between HCl and NaOH is:

HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

The mole ratio between HCl and NaOH is 1:1. Using this ratio, the amount of moles of NaOH used in the titration can be calculated as follows:

Moles NaOH = Molarity NaOH x Volume NaOH (in liters)

Moles NaOH = 0.0900 M x 0.03100 L = 0.00279 moles

Since the mole ratio between HCl and NaOH is 1:1, moles HCl = moles NaOH.

Therefore, moles HCl = 0.00279 moles.

To find the molarity of the HCl, we divide the moles of HCl by the volume of HCl solution used (in liters):

Molarity HCl = Moles HCl / Volume HCl (in liters)

Molarity HCl = 0.00279 moles / 0.01000 L = 0.279 M

Answer 2

Molar concentration of HCl = 0.279 M

Step-by-step explanation:

Given data:

Volume of NaOH = 31.00 mL ( 31/1000 = 0.031 L)

Molarity of NaOH = 0.0900 M

Volume of HCl = 10.00 mL (0.01 L)

Molar concentration of HCl = ?

Solution:

Chemical equation:

NaOH + HCl → NaCl + H₂O

Number of moles of NaOH:

Number of moles = Molarity × volume in L

Number of moles = 0.0900 mol/L × 0.031 L

Number of moles = 0.00279 mol

For one mole of HCl one mole of NaOH is required.

Number of moles of HCl = 0.00279 mol

Molar concentration of HCl = 0.00279 mol / 0.01 L

Molar concentration of HCl = 0.279 M