Question

How many molecules of oxygen are present in 1ltr air containg 80 percent volume of o2 at stp?

Answer 1

Percentage of oxygen in air is 80%

percentage = volume of the oxygen/volume of air ×100

80 = volume of oxygen/1L × 100

80L × 1/100 = volume of oxygen

0.8L = volume of oxygen

[or you can directly do it like in 1L air percentage of oxygen is 80 means 0.8L oxygen and 0.2L other substance]
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We know that one mole of any substance contains 22.4L volume in STP (standard temperature and pressure) so,

volume = number of moles ×22.4

volume/22.4 = number of moles

0.8/22.4 = number of moles

0.036 = number of moles
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we know that one mole of any substance contains 6.022×10^23 molecules.

molecules = number of moles × 6.022×10^23

molecules = 0.036 × 6.022 × 10^23

molecules = 0.216 × 10^23

molecules = 2.16 × 10^22 " O2 molecules ”
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use can directly find it use this formula
molecules = volume of substance/22.4 × 6.022×10^23

Answer 2

Answer:

Answer: 2.15x 10^22 molecules.

Explanation:

▪️ Correct question should be: how many molecules of oxygen are present in 1 litre of air containing 80% of O2.

First, we will have to find amount of energy in one oxygen.

Therefore,

➡️ Amount of oxygen present in 1 litre air is = 80% *1000 ml

➡️ (80/100)*1000

=800ml

▪️ We know that, 1 mole of STp occupies 22.4 litre

It is equal to = 22400ml of O2 gas contains 6.022x 10^23 molecules

So,

➡️ 1ml of O2 gas Contains =6.022x10^23/22400

According to question, we have to find 800ml molecules.

Therefore,

800ml contains =(6.022x 10^23/22400) *800

=> 2.15 x 10^22

▪️ Hence, molecules present in 1 litre air containing 80% volume of at STP is 2.15x 10^22 molecules.