Question

The amount of gas (in terms of moles, mass, and molecules)

Answer 1

Short summary and the formulas you need

- Symbols/definitions:
- n = amount of substance (moles, mol)
- m = mass of sample (g or kg)
- M = molar mass (g·mol−1 or kg·mol−1)
- N = number of molecules (or particles)
- NA = Avogadro’s number = 6.02214076 × 10^23 mol−1

- Key relations:
- n = m / M
- N = n × NA
- m = n × M = N × (M / NA)
- mass of one molecule = M / NA (in g if M in g·mol−1; convert to kg by dividing by 1000)

- If volume/pressure/temperature are given (ideal gas):
- PV = nRT → n = PV / (RT)
- R = 0.082057 L·atm·mol−1·K−1 or 8.314462618 J·mol−1·K−1

Examples
- 2.50 mol O2 (M = 32.00 g·mol−1):
- mass m = 2.50 × 32.00 = 80.0 g
- molecules N = 2.50 × 6.022×10^23 = 1.51×10^24 molecules

- 10.0 g N2 (M = 28.02 g·mol−1):
- n = 10.0 / 28.02 = 0.357 mol
- N = 0.357 × 6.022×10^23 = 2.15×10^23 molecules

- mass of one CO2 molecule (M = 44.01 g·mol−1):
- m_one = 44.01 / 6.022×10^23 = 7.31×10^−23 g = 7.31×10^−26 kg

If you want, tell me the gas and the quantity you have (mass, moles, volume at given P & T, or number of molecules) and I’ll convert it for you.