How many grams of 12M HCl is needed to make up 100g of a 5% aqueous solution of hydrochloric acid

To solve this problem, we'll break it down step by step.

### 1. Determine the mass of HCl needed in the 5% solution:
A 5% aqueous solution of hydrochloric acid means that 5% of the total mass of the solution is pure HCl. 

Given:
- Total mass of the solution = 100 g
- Percentage of HCl in the solution = 5%

The mass of HCl needed:
\[
\text{Mass of HCl} = \frac{5}{100} \times 100\,\text{g} = 5\,\text{g}
\]

So, 5 grams of HCl is required in the final solution.

### 2. Calculate the mass of 12M HCl solution required to provide 5 grams of HCl:

Given:
- Concentration of the HCl solution = 12M
- Molar mass of HCl = 36.46 g/mol

First, calculate the number of moles of HCl needed:
\[
\text{Moles of HCl} = \frac{5\,\text{g}}{36.46\,\text{g/mol}} \approx 0.137\,\text{moles}
\]

Now, determine the mass of the 12M HCl solution needed:
- Since 1 liter of 12M HCl contains 12 moles of HCl, the mass of HCl solution needed can be calculated as follows:
\[
\text{Volume of 12M HCl needed} = \frac{0.137\,\text{moles}}{12\,\text{moles/L}} \approx 0.0114\,\text{L} = 11.4\,\text{mL}
\]

Since the density of 12M HCl solution is approximately 1.18 g/mL, the mass of the 12M HCl solution required:
\[
\text{Mass of 12M HCl solution} = 11.4\,\text{mL} \times 1.18\,\text{g/mL} \approx 13.5\,\text{g}
\]

### Final Answer:
You need approximately **13.5 grams** of 12M HCl solution to make 100 grams of a 5% aqueous solution of hydrochloric acid.

Would you like more details or have any questions?

Here are 5 related questions to consider:
1. How would the mass of HCl needed change if the solution concentration was 10% instead of 5%?
2. What is the significance of the molarity in calculating the amount of solution needed?
3. How would you prepare the 5% solution if you only had 6M HCl instead of 12M?
4. What are the safety considerations when handling concentrated HCl?
5. How does the density of the HCl solution affect the calculation?

**Tip:** Always ensure to use proper personal protective equipment (PPE) when handling strong acids like HCl, including gloves and eye protection.

Learn how to calculate the amount of 12M HCl solution required to make a 5% aqueous solution of hydrochloric acid. This problem involves calculating the mass of HCl needed, molarity calculations, and percentage concentration. Suitable for advanced high school chemistry students.

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