Question

calculate the no of moles in 17g of H2O2.

Answer 1

Number of moles =  $\frac{Given\:Mass}{Molar\:Mass}$

Given mass = 17g (Given in Question)

Q. What is Molar mass?

⇒ Total mass of each atom in that compound i.e. the mass of a given substance divided by the amount of substance.

The base SI unit for molar mass is kg/mol.   (Note It's not mole, Its mol here because, In Formula we use mol.)

Molar Mass = H₂O₂ = $1u \times 2 + 16u \times 2$

Molar mass = 2 + 32 u

Molar mass = 34 u.

Putting the values in formula,

We get ;  

Number of moles =  $\frac{Given\:Mass}{Molar\:Mass}$

⇒ Number of moles =  $\frac{17}{34}$

⇒ Number of moles =  $\frac{1}{2}$ moles.

or

⇒ Number of moles =  0.5 moles

Thanks!

Answer 2

given
h=1u
o=16u
at stp 1 mole of hydrogen contains 6.023×10^23 molecules

x= 17×6.023×10^23
17/10=6.023×10^23/x
17/x=6.023×10^23×10
17g=6.023×10^24

17g of h202 contains 6.023×10^24 molecules

hope it will be useful for u