The titration of a 20.0 mL sample of an H2SO4 solution of unknown concentration requires 22.87 mL of a 0.158 M KOH solution to reach the equivalence point. What is the concentration of the unknown H2SO4 solution?

Respuesta :

The concentration of 20.0 mL H2SO4 solution that requires 22.87 mL of a 0.158 M KOH solution to reach equivalence point is 0.0904 M. or 0.0904 moles/L

Further Explanation:

Molarity  

  • Molarity may be defined as the concentration of a solution in moles per liter. It is calculated by dividing the number of moles of a solution, n by its volume in liters, V.  
  • That is; Molarity = n/V, where n is the number of moles and V is the volume in liters.  
  • Therefore; when given the molarity of a solution and the volume of the solution, then we can get the number of moles, by multiplying the molarity by volume;  
  • Number of moles = Molarity x Volume
  • Additionally, the number of moles of a compound or an element can also be calculated by dividing the mass of the compound by its relative molecular mass.

In the question given;

The equation for the reaction is:

H2SO4 + 2KOH = K2SO4 + 2H2O

Step 1: Moles of KOH  

Number of moles = Molarity x Volume  

Molarity of KOH is 0.158 M  

Volume of KOH is 22.87 mL or 0.02287 L

Therefore;

Number of moles = 0.158 M x 0.02287 mL

                            = 0.003613 Moles of KOH  

Step 2: Moles of H2SO4

Mole ratio; from the equation, 1 mole of H2SO4 requires 2 moles of KOH

Therefore;

0.003613 moles of KOH requires  

   = 0.003613/2  

   = 0.001807 Moles  

Step 3: Molarity of H2SO4

Molarity = Number of moles / Volume  

Number of moles = 0.001807 moles  

Volume = 20 mL or 0.020 L  

Therefore;

Concentration = 0.001807/ 0.020  

                       = 0.0904 M

Hence, the concentration of the acid, H2SO4 was 0.0904 M or 0.0904 moles/L

Keywords: Molarity, Moles, Volume

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Level: High School

Subject: Chemistry

Chapter: Mole and stoichiometry equations

The concentration of the unknown H₂SO₄ solution is 0.09 M

Balanced equation

H₂SO₄ + 2KOH —> K₂SO₄ + 2H₂O

From the balanced equation above,

  • The mole ratio of the acid, H₂SO₄ (nA) = 1
  • The mole ratio of the base, KOH (nB) = 2

How to determine the concentration of H₂SO₄

  • Volume of acid, H₂SO₄ (Va) = 20 mL
  • Volume of base, KOH (Vb) = 22.87 mL
  • Concentration of base, KOH (Cb) = 0.158 M
  • Concentration of acid, H₂SO₄ (Ca) =?

CaVa / CbVb = nA / nB

(Ca × 20) / (0.158 × 22.87) = 1 / 2

(Ca × 20) / 3.61346  = 1 / 2

Cross multiply

Ca × 20 × 2 = 3.61346

Ca × 40 = 3.61346

Divide both side by 40

Ca = 3.61346 / 40

Ca = 0.09 M

Thus, the concentration of the H₂SO₄ solution is 0.09 M

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