# Calculate:(a) The number of moles of Sulphur (S8) present in 16 g of solid sulphur.(b) the mass of 10 moles of sodium sulphite (Na2SO3).(c) the number of atoms in 11.5 g of Na.[atomic mass: Na = 23u; S = 32u, O = 16u, NA = 6.022 × 1023 mol–1]

a) Given:

Mass of sulphur (m) = 16g

Atomic mass of sulphur (S8) = 8 × 32u = 256 u

Molar mass of S8 (M) = 256g/mol

To calculate the number of moles, we will apply the formula given below:  Number of moles = 0.0625

Thus, the number of moles in 16 g of solid sulphur is 0.0625.

b) Given:

Number of moles = 10

Molecular mass of sodium sulphite (Na2SO3) = 2 × Atomic mass of Na + atomic mass of sulphur + 3 × Atomic mass of O

= 2 × 23 u + 32 u + 48 u

= 126 u

Molar mass of Na2SO3 = 126g/mol

To calculate the mass, apply the formula: We can write:

Mass = Number of moles × Molar mass

Mass = 10 mol × 126g/mol

Mass = 1260g

Thus, the mass of sodium sulphite is 1260g.

c) Given:

Mass of Na (m) = 11.5g

Atomic mass of sulphur = 23u

Molar mass of sulphur (M) = 23g/mol

To calculate the number of moles, we will apply the formula given below:  Number of moles = 0.5

We know, 1 mole = 6.022 × 1023(Na = Avogadro’s number) We can write, number of atoms = Number of moles × Na

Number of atoms = 0.5 × 6.022 × 1023

Number of atoms = 3.022 × 1023

Thus, the number of atoms in 11.5 g of Na is 3.022 × 1023

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos  NCERT Exemplar | Atoms and Molecules48 mins  NCERT Exemplar | Atoms and Molecules43 mins  Mastering in Valency33 mins  Types of Bonding29 mins  Smart Revision | Basic Concept of Mole51 mins  Quiz | Solve Imp. Qs. on Ions,Molecules and Compounds26 mins  Smart Revision | Master the Art of Writing Chemical Formulae46 mins  Atomic Models53 mins  NCERT | Laws of Chemical Combinations - I43 mins  Champ Quiz | Are you a Master of Mole Concept ?35 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation view all courses 