Question

Example 3.3
1. Calculate the number of moles for the
following:
(i) 52 g of He (finding mole from
mass)
(ii) 12.044 x 1023 number of He atoms
(finding mole from number of
particles).​

Answer 1

Answer:

I) mole of He = weight / molar mass. here molar mass of He is 4 then mole of He = 52/4 , mole of He =13 . ii) no.of he atom= mole of He ×avagadro no. :::::: avagadro no. is 6.022×10^23 then ... 12.044×10^23=mole of He ×6.022×10^23 after solving mole of He is 2

Answer 2

Answer:2

• Explanation:No. of moles = n
• Given mass = m
• Molar mass = M
• Given number of particles = N
• Avogadro number of particles = N0
• (i) Atomic mass of He = 4 u
• Molar mass of He = 4g
• Thus, the number of moles
• = given mass molar mass
• ⇒n=mM=524=13
• (ii) we know,
• 1 mole = 6.022×1023
• The number of moles
• = given number of particles Avogadro number

⇒n=N No=12.044×10236.022×1023=2