Question

Normality of concentrated HCl (37%) with density 1.19 g/mL is approximately 12. What volume of the same is required to prepare 500 mL of 0.3 N HCl?

• A. 1.25ml
• B. 2.59ml
• C. 3.52ml
• D. 12.5ml

Answer 1

Answer:

D. 12.5ml

• Normality (N) is defined as the number of gram equivalents of solute per liter of solution. It is a measure of concentration.

• For acids like HCl, the equivalent weight is its molar mass divided by its basicity (number of ionizable hydrogen atoms). For HCl, the basicity is 1, so the equivalent weight is equal to its molar mass (approximately 36.5 g/mol).

Concentrated HCl Information

• The given concentrated HCl has a purity of 37% by mass.

• Its density is 1.19 g/mL.

• The calculated normality of this concentrated acid is approximately 12 N. This means 1 liter of this concentrated solution contains approximately 12 gram equivalents of HCl.

Dilution Principle (Using Normality)

• The principle used for dilution is that the number of gram equivalents of solute remains the same before and after dilution.

• This can be expressed by the formula: N₁V₁ = N₂V₂

  • N₁ = Normality of the concentrated solution (stock solution)

  • V₁ = Volume of the concentrated solution required

  • N₂ = Normality of the desired dilute solution

  • V₂ = Final volume of the desired dilute solution

Applying the Formula

• We need to prepare 500 mL (0.5 L) of 0.3 N HCl.

• So, N₂ = 0.3 N and V₂ = 500 mL.

• The concentrated HCl has a normality of approximately N₁ = 12 N.

• Substitute these values into the formula:
  12 N * V₁ = 0.3 N * 500 mL

• Now, solve for V₁:
  V₁ = (0.3 N * 500 mL) / 12 N

• V₁ = 150 mL / 12

• V₁ = 12.5 mL