Question

if gases a,b,c are arranged in increasing order of their RMM and the mass of each gas is 10g at S.T.P . State which gas will contain the least no of molecules and which the most​

Answer 1

Answer:

• Gas 'c' has the maximum number of molecules
• Gas 'a' has the least number of molecules

Explanation:

We know that

Number of molecules = Number of moles × Avogadro Number

⇒ Number of molecules ∝ Number of moles

⇒ Number of molecules ∝ Mass ÷ RMM

Here, all gases have the same mass that is 10g.

So, we can ignore the mass and write the equation as

Number of molecules ∝ 1 ÷ RMM

Gases a, b, c are arranged in the increasing order of RMM.

So, these gases are arranged in the decreasing order of the number of molecules.

This means that

• Gas 'c' has the maximum number of molecules.
• Gas 'a' has the least number of molecules.

Answer 2

1 Mole of gas 'A' weighs X'g/ [REL MOL MASS) contains 6.023 x 10²³

10 g. of gas 'A' contains 6.023 x 10²³ x 10/'X' molecules

Since gases A, B and 'C are in increasing order of relative molecular mass we assume the w molecular mass of gas 'B' as 2X and gas 'C' as '3X'.

Hence,

10 g. of gas B contains 6.023 x 10²³ x 10/2X molecules

&

10 g. of gas 'C' contains 6.023 x 10²³x10/3X molecules

Gas 'C' contains least number

gas 'A' the maximum no. of molecules. - Ans.