What mass will 2.5 L of chlorine gas be at STP?

Answer: m = 7.7 g Cl2

Explanation: To find mass of chlorine gas we will first derive the ideal gas law formula and find first the number of moles of Cl2. At STP, Pressure is equal to 1 atm and temperature is 273 K.

n = PV / RT

= 1 atm (2.5 L) / 0.0821 L. atm / mole. K (273 K)

= 0.11 mole Cl2

Convert moles of Cl2 to grams using the molar mass of Cl2 which is 70 g Cl2.

0.11 mole Cl2 x 70 g Cl2 / 1 mole Cl2

= 7.7 g Cl2

One mole of any gas at STP takes up 22.4 L

1 mole of gas = 22.4L

2.5 moles of gas takes up = (22.4 L / 1 mole) x 2.5 mole

= 56 L