A cylinder of oxygen (O2) gas at STP has a volume of 2.75 L. How many oxygen molecules does it contain?

7.40×10²² molecules.

Explanation:

From the question given above, the following data were obtained:

Volume of oxygen = 2.75 L

Number of molecules of oxygen =?

Next, we shall determine the number of mole of oxygen present. This can be obtained as follow:

22.4 L contains 1 mole of oxygen at STP.

Therefore, 2.75 L will contain = 2.75 / 22.4 = 0.123 mole of oxygen at STP.

Finally, we shall determine the number of molecules of oxygen present. This can be obtained as follow:

From Avogadro's hypothesis:

1 mole of oxygen = 6.02×10²³ molecules

Therefore,

0.123 mole of oxygen = 0.123 × 6.02×10²³

0.123 mole of oxygen = 7.40×10²² molecules.

Thus, the cylinder contains 7.40×10²² molecules of oxygen.

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explanation: