At standard temperature and pressure (STP), the conditions are defined as a temperature of 0 degrees Celsius (273.15 Kelvin) and a pressure of 1 atmosphere (101.325 kilopascals).
To find the amount of substance (moles) of CO₂ in 2.8 dm³, we can use the ideal gas law equation:
PV = nRT
Where: P = Pressure (in atmospheres) V = Volume (in liters) n = Amount of substance (in moles) R = Ideal gas constant (0.0821 L·atm/(mol·K)) T = Temperature (in Kelvin)
Plugging in the values: P = 1 atm V = 2.8 dm³ = 2.8 liters R = 0.0821 L·atm/(mol·K) T = 273.15 K (standard temperature)
PV = nRT
(1 atm) * (2.8 L) = n * (0.0821 L·atm/(mol·K)) * (273.15 K)
2.8 = n * (0.0821 * 273.15)
2.8 = n * 22.414
n = 2.8 / 22.414
n ≈ 0.125 moles
So, the amount of substance of CO₂ in 2.8 dm³ at STP is approximately 0.125 moles.
To find the mass of the gas, we need to know the molar mass of CO₂, which is 44.01 grams/mol.
Mass = moles * molar mass
Mass = 0.125 moles * 44.01 g/mol
Mass ≈ 5.50125 grams
Therefore, the mass of the CO₂ gas in 2.8 dm³ at STP is approximately 5.50125 grams.
To find the number of molecules, we can use Avogadro's number, which is approximately 6.022 x 10²³ molecules/mol.
Number of molecules = moles * Avogadro's number
Number of molecules = 0.125 moles * 6.022 x 10²³ molecules/mol
Number of molecules ≈ 7.5275 x 10²² molecules
Therefore, there are approximately 7.5275 x 10²² molecules of CO₂ gas in 2.8 dm³ at STP.