Question

The end point in a titration of a 52ml sample of aqueous (HCl) was reached by addition of 42ml of 0.23M titrant.

The titration reaction is

2HCl+Ba(OH)₂→BaCl₂+2H₂O

What is the molar concentration of (HCl)? Give your answer in two significant figures.

Answer 1

The balanced chemical reaction is as follows:

2HCl(aq) + Ba(OH)₂(aq) BaCl₂(aq) + 2H₂O(l)

Concentration of titrant[Ba(OH)₂] = 0.23 M

Volume of titrant[Ba(OH)₂] = 42 mL x ( 1 L /1000 mL) = 0.042 L

Volume of aqueous HCl = 52 mL x ( 1L /1000 mL) = 0.052 L

Determine the number of moles of Ba(OH)₂ from the given concentration and volume as follows:

Molarity = Number of moles / Volume(L)

Rearranging the formula for number of moles as follows:

Number of moles = Molarity x Volume(L)

Number of moles of Ba(OH)₂= 0.23 M x 0.042 L = 0.00966 mol Ba(OH)₂

Use the moles of Ba(OH)₂ and the mole ratioi from the balanced chemical reaction and determine the number of moles of HCl as follows:

= 0.00966 mol Ba(OH)₂ x (2 mol HCl / 1 mol Ba(OH)₂)

= 0.01932 mol HCl

Use the formula of molarity and determine the concentration of HCl as follows:

Molarity = Number of moles / Volume(L)

Molarity = 0.01932 mol HCl /0.052 L

Molarity = 0.372 M

Thus, the molar concentration of HCl is 0.37 M [ 2S.F]