WILL MARK BRAINLIST!! A chemist weighs a steel cylinder of compressed oxygen, O2, and finds that it has a mass of 1027.8 g. After some of the oxygen is used in an experiment, the cylinder has a mass of 1023.2 g. How many moles of oxygen gas are used in the experiment?

When answering this question include the following:

Explain how you found the mass of oxygen gas.
Explain how to find the molar mass of the compound.
Explain how many significant figures your answer needs to have.
The numerical answer

To find the amount of moles lost, (1) convert the grams O₂ before to moles (via molar mass from periodic table), then (2) convert the grams O₂ after to moles, then (3) subtract the moles O₂ after from the moles O₂ before.

Molar Mass (O₂) = 2(15.999) g/mol

Molar Mass (O₂) = 31.998 g/mol

Before Experiment:

1,027.8 grams O₂ 1 mole O₂
-------------------------- x ---------------------- = 32.121 moles O₂
31.998 grams

After Experiment:

1,023.2 grams O₂ 1 mole O₂
-------------------------- x ---------------------- = 31.977 moles O₂
31.998 grams

Moles Before - Moles After = Moles Lost

32.121 moles - 31.977 moles = 0.14376 moles O₂

The number of significant figures is determined by the significant figures of the values given. Both of the given values (1,027.8 and 1,023.2) have 5 sig figs. Therefore, the answer should also have 5 sig figs.