1. Understand STP
STP stands for Standard Temperature and Pressure. It is defined as:
* Temperature: 0°C (273.15 K)
* Pressure: 1 atm (101.325 kPa)
2. Use the Ideal Gas Law
The Ideal Gas Law relates pressure (P), volume (V), number of moles (n), the gas constant (R), and temperature (T):
PV = nRT
3. Determine the Molar Mass of Ethane (C₂H₆)
* Carbon (C) has a molar mass of 12.01 g/mol
* Hydrogen (H) has a molar mass of 1.01 g/mol
* Ethane (C₂H₆) has a molar mass of (2 * 12.01) + (6 * 1.01) = 30.07 g/mol
4. Calculate the Number of Moles (n)
* Convert the volume from mL to L: 455 mL = 0.455 L
* Rearrange the Ideal Gas Law to solve for n: n = PV / RT
* Use the appropriate value for the gas constant R: 0.0821 L·atm/(mol·K)
* Plug in the values: n = (1 atm * 0.455 L) / (0.0821 L·atm/(mol·K) * 273.15 K)
* Calculate: n ≈ 0.0204 moles
5. Calculate the Mass
* Multiply the number of moles by the molar mass of ethane: mass = n * molar mass
* mass ≈ 0.0204 moles * 30.07 g/mol
* mass ≈ 0.614 g
Therefore, the mass of 455 mL of ethane gas at STP is approximately 0.614 grams.
