What is the approximate density (in g/mL) of chlorine gas (Cl₂) at STP?
(a) 3.2 g/mL
(b) 3.2 x 10⁻³ g/mL
(c) 3.2 x 10³ g/mL
(d) 4.5 x 10⁻³ g/mL
(e) 6.2 g/mL



Answer :

Answer:

(b) 3.2 x 10⁻³ g/mL

Explanation:

At STP (Standard temperature and pressure), the volume that a gas takes up is 22.4 L. Since density measures mass divided by volume, we can take the molar mass of chlorine gas and divide it by the volume at STP. Make sure to note that our answer should be in mL and not L.

Solving:

[tex]\text{The molar mass of \(\text{Cl}_2\) (chlorine gas)}:\\\\\[\text{Molar mass of Cl}_2 = 2 \times 35.5 \, \text{g/mol} = \boxed{71 \, \text{g/mol}}\][/tex]

[tex]\text{To find the density (\(\rho\)) of \(\text{Cl}_2\) gas at STP, we can use the formula for density:}\\\\\[\rho = \frac{\text{mass}}{\text{volume}}\][/tex]

[tex]\[\rho = \frac{71 \, \text{g/mol}}{22.4 \, \text{L/mol}}\][/tex]

[tex]\[22.4 \, \text{L} = 22,400 \, \text{mL}\][/tex]

[tex]\[\rho = \frac{71 \, \text{g}}{22,400 \, \text{mL}}\][/tex]

[tex]\[\rho \approx 3.17 \times 10^{-3} \, \text{g/mL}\][/tex]

Round to two significant figures:

[tex]\[\boxed{3.2 \times 10^{-3} \, \text{g/mL}}\][/tex]