What is an ideal gas? Give one reason why a real gas like carbon dioxide deviates from ideal behaviour - Leaving Cert Chemistry - Question a - 2006

One reason carbon dioxide deviates from ideal behaviour is due to intermolecular forces. Real gases experience attractions between molecules, known as intermolecular forces, which can lead to deviations from the predictions of ideal gas behavior, particularly at high pressures and low temperatures.

To calculate the number of moles, we use the ideal gas equation:

$PV = nRT$

Where:

• P = pressure in pascals = $1 imes 10^2$ Pa
• V = volume in cubic meters = $720 ext{ cm}^3 = 0.00072 ext{ m}^3$
• R = ideal gas constant = $8.31 ext{ J/(mol K)}$
• T = temperature in kelvins = $10 °C + 273.15 = 283.15 ext{ K}$

Plugging in the values:

n = rac{PV}{RT} = rac{(1 imes 10^2) imes (0.00072)}{(8.31) imes (283.15)}

Calculating this gives:

$n ext{ (moles)} = 0.03 ext{ mol}$

Thus, the number of moles of carbon dioxide present is 0.03 mol.

To find the number of molecules, we use Avogadro's number, which is approximately $6.022 imes 10^{23}$ molecules/mol. The calculation is as follows:

$ext{Number of molecules} = n imes N_A = 0.03 imes 6.022 imes 10^{23}$

Calculating this gives:

$ext{Number of molecules} ext{ (CO}_2 ext{)} = 1.8 imes 10^{22} ext{ molecules}$

From the balanced chemical equation: