Prepare 1M HCl; the purity of HCl is 36%.
Understand the Problem
The question is asking how to prepare a 1 molar solution of hydrochloric acid (HCl) from a stock solution that has a purity of 36%. It implies a need for calculations to determine how much of the concentrated solution is required to dilute to the desired molarity.
Answer
To prepare a 1 M solution of hydrochloric acid, use approximately 101.3 mL of the concentrated HCl stock solution diluted to 1 L.
Answer for screen readers
To prepare a 1 M solution of hydrochloric acid from a 36% stock solution, take approximately 101.3 mL of the concentrated HCl.
Steps to Solve
- Identify the desired molarity and the concentration of the stock solution
The desired molarity of the hydrochloric acid solution is 1 M (molar). The stock solution is 36% concentrated HCl, which means it has 36 grams of HCl in 100 mL of solution.
- Calculate the molarity of the stock solution
First, convert the percentage concentration to molarity. The molar mass of HCl is approximately 36.46 g/mol.
Using the formula for molarity: $$ M = \frac{\text{mass (g)}}{\text{molar mass (g/mol)} \times \text{volume (L)}} $$
Using the 36 g of HCl in 100 mL (or 0.1 L): $$ \text{Molarity of stock solution} = \frac{36 , \text{g}}{36.46 , \text{g/mol} \times 0.1 , \text{L}} $$
- Calculate the result from the stock solution's molarity
Now perform the calculation from the previous step: $$ M_{stock} = \frac{36}{36.46 \times 0.1} = \frac{36}{3.646} \approx 9.87 , \text{M} $$
- Use the dilution formula to find the volume of stock solution needed
Use the dilution formula: $$ C_1V_1 = C_2V_2 $$
Where:
- $C_1$ = molarity of stock solution = 9.87 M
- $V_1$ = volume of stock solution needed
- $C_2$ = desired molarity = 1 M
- $V_2$ = final volume of solution (to be determined)
Let's say we want to prepare 1 L (or 1000 mL) of a 1 M solution: $$ 9.87 , \text{M} \times V_1 = 1 , \text{M} \times 1 , \text{L} $$
- Calculate the volume of the stock solution needed
Rearranging the formula to find $V_1$ gives: $$ V_1 = \frac{1 , \text{M} \times 1 , \text{L}}{9.87 , \text{M}} $$
Now perform the calculation: $$ V_1 \approx \frac{1}{9.87} \approx 0.1013 , \text{L} \approx 101.3 , \text{mL} $$
- Prepare the solution
Measure approximately 101.3 mL of the concentrated HCl stock solution and dilute it with distilled water to a final volume of 1 L to create a 1 M solution.
To prepare a 1 M solution of hydrochloric acid from a 36% stock solution, take approximately 101.3 mL of the concentrated HCl.
More Information
To dilute concentrated hydrochloric acid safely, always add the acid to water, not the other way around, to avoid exothermic reactions that can cause splattering.
Tips
- Not using the correct molar mass for calculations: Always verify the molar mass of the compound.
- Forgetting to convert mL to L when calculating molarity: It's important to use the same units in the equations.
- Miscalculating the final volume needed for dilution: Ensure you measure the final solution volume accurately.