Calculating the Number of Moles in 1200 mL of Hydrochloric Acid (HCl) at RTP

Hydrochloric acid (HCl) is a strong acid commonly used in various chemical applications. Determining the number of moles in a given volume of HCl gas, especially under standard conditions like room temperature and pressure (RTP), is a fundamental skill in chemistry. However, it is crucial to clarify the units of the given volume to perform accurate calculations.

Units Clarification

The problem provided does not specify the units for 1200.00 mL of HCl. Without a unit, it is ambiguous whether the volume is in grams (g), milliliters (mL), cubic meters (m3), or another unit. To proceed, it is necessary to assume a consistent and sensible unit that makes sense in the context of gaseous HCl at RTP (room temperature and pressure).

Calculation at RTP

At RTP, one mole of a gas occupies a volume of 24.0 liters (L).

Calculation Example 1

Given: Volume of HCl gas 1200 mL 1.2 L

Knowing that one mole of HCl gas occupies 24.0 L at RTP, the number of moles can be calculated as follows:

No. of moles Volume (L) / Molar Volume (L/mol) 1.2 L / 24.0 L/mol 0.05 mol

Calculation Example 2

Molar volume at RTP is often stated as 24.0 liters per mole (L/mol), although some sources may give 24.5 L/mol.

Using the molar volume of 24.0 L/mol for HCl gas:

No. of moles Volume (L) / Molar Volume (L/mol) 1.2 L / 24.0 L/mol 0.05 mol

Calculation Example 3

Another common approximation is to assume that 1.00 mol of HCl gas has a volume of 24.0 L (24,000 mL), which converts to 24,000 milliliters (mL).

No. of moles Volume (L) / Molar Volume (L/mol) 1.2 L / 24.0 L/mol 0.05 mol

Calculation Example 4

Using 24.5 L/mol for the molar volume at RTP:

No. of moles Volume (L) / Molar Volume (L/mol) 1.2 L / 24.5 L/mol ≈ 0.049 mol

These calculations assume that the HCl gas is behaving ideally under RTP conditions. The slight difference in the molar volume (24.0 L/mol vs. 24.5 L/mol) reflects the fact that real gases may deviate from ideal behavior. However, for most practical purposes, using 24.0 L/mol provides a sufficiently accurate calculation.

Conclusion

In summary, the number of moles in 1200 mL of HCl gas at RTP can be calculated by dividing the volume (1.2 L) by the molar volume (24.0 L/mol or 24.5 L/mol). The resulting value is 0.05 mol, with small variations depending on the assumed molar volume. This calculation is essential for a wide range of chemical applications, including stoichiometric reactions, titrations, and gas laws.