Answer: 16g/mol; O2
Explanation:
The gas has a volume of 2.5L at STP, so the number of moles can be determined as follows.
n=2.5L×1mol/22.4L=0.1116mol
The mass is given to be 3.571g. The molar mass of the unknown gas can be determined by dividing grams by moles.
3.571g/0.1116mol=32.00g/mol
The gas is a homonuclear diatomic gas, so the gas must contain two atoms with a molar mass of 32g/mol/2=16g/mol. This is the molar mass of the element oxygen, so the gas is diatomic oxygen, O2.
The molecular formula of the gas is O₂
We'll begin by calculating the number of mole of the gas that occupied 2.5 L at stp. This can be obtained as follow:
22.4 L = 1 mole of a gas
Therefore,
2.5 L = 2.5 / 22.4
Next, we shall determine the molar mass of the gas. This can be obtained as follow:
Mass of gas = 3.571 g
Mole of gas = 0.1116 mole
[tex]Mole = \frac{mass}{molar mass} \\\\0.1116 = \frac{3.571}{molar mass }[/tex]
Cross multiply
0.1116 × molar mass = 3.571
Divide both side by 0.1116
Molar mass = [tex]\frac{3.571}{0.1116}\\\\[/tex]
Since the gas is a homonuclear diatomic gas (i.e a molecule of the same element), the molar mass of the element that makes up the gas = 32/2 = 16 g/mol
Comparing the molar mass of the element (i.e 16 g/mol) that makes up the gas with those in the periodic table, the element is oxygen.
Therefore the gas is oxygen gas and the molecular formula is O₂
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