Question

at stp, 18 l of o₂ would have a mass of how many grams?
13 g
26 g
40 g
1300 g

Explanation:

Step1: Calculate the number of moles of \(O_2\)

At STP (Standard Temperature and Pressure), 1 mole of any ideal gas occupies 22.4 L.
The number of moles \(n\) of \(O_2\) is given by \(n=\frac{V}{V_m}\), where \(V = 18\space L\) and \(V_m=22.4\space L/mol\)
\(n=\frac{18}{22.4}\space mol\approx0.8036\space mol\)

Step2: Calculate the molar mass of \(O_2\)

The molar mass \(M\) of \(O_2\) (since the atomic mass of \(O\) is \(16\space g/mol\)) is \(M = 2\times16=32\space g/mol\)

Step3: Calculate the mass of \(O_2\)

The mass \(m\) of \(O_2\) is given by \(m=n\times M\)
Substitute \(n = 0.8036\space mol\) and \(M = 32\space g/mol\)
\(m=0.8036\times32\space g\approx25.72\space g\approx26\space g\)

Answer:

26 g