Question

what is the no. of molecules of co2which contains 8 g of o2​

Answer 1

$\huge\mathfrak{Answer}$

Number of molecules = 1.5055 × 10²³

$\huge\textsf{Explanation}$

We know that atoms join together to form molecule in a constant proportion by mass.

Here, we need to find the ratio of mass of Carbon to oxygen, in order to find the mass of carbon dioxide.

So, mass of one atom of carbon = 12 u

mass of one atom of O = 16 u

⇒ O₂ = 32 u

So, their ratio by mass = 12 :32

⇒ 3 : 8

So, here we are given that mass of oxygen is 8 grams. Now, let the mass of carbon be x grams.

So, according to the law of constant proportion, we get

3 : 8 :: x : 8

⇒ x = 3 grams

So, we get mass of carbon as 3 grams

Now, mass of given carbon dioxide = mass of C + mass of O₂

⇒ mass of given CO₂ = 3 + 8 = 11 g

And, we know that molar mass of CO₂ = 44 g (since molar mass of C = 12 g, and molar mass of O₂ = 32 g, we get molar mass of CO₂ as 44 g)

So, mole = given mass/molar mass

⇒ mole = 11/44

⇒ mole = 1/4

Now, number of molecules = mole × avogadro number

⇒ Number of molecules = 1/4 × 6.022 × 10²³

⇒ Number of molecules = 1.5055 × 10²³

$\rule{200}2$