Question

On a cold day near the ocean it was found that 8g of an unknown gas occupies a volume that is a little less than 6 l. based on this information, what is the most likely identity of the unknown gas

Answer 1

Answer: O₂.


Step-by-step explanation:


1) This question has four answer choices:

A) CO₂
B) Ne
C) O₂
D) CH₄


2) You are told that it is a cold day and that the volume is a litle less than 6 liters, then you don't know either the exact temperature or the exact volume, which means that you can only make estimations.


3) Using the fact that 1 mol of a gas occupies 22.4 liters at standard conditions (273K and 1 atm), you can estimate the number of moles from the proportion:


1 mol / 22.4 l = x / 6 l ⇒ x = 1 mol x 6 l / 22.4 l = 0.2679 moles


4) Now you can estimate the molar mass from the formula molar mass = mass in grams / number of moles


molar mass = 8g / 0.2679 moles = 29.9 g/mol


5) The molar masses of the 4 gases indicated are:


CO₂: 44 g/mol

Ne: 20 g/mol

O₂: 32 g/mol

CH₄: 16g/mol


6) Conclusion: the only choice that is a match is O₂.

Answer 2

Know that at 0 degree celsius 1 mol of gas occupies 22.4L

molar volume is
Vm = 22.4L / moles

number of moles:

6L / (22.4 L / mol) = 0.2679 mol

The molar mass of this gas:

molar mass = 8g / 0.2679 mol = 29.9 g/mol

The value is around 32 mg/mol (which is the molar mass of oxygen)

Thus,

The answer is O2