Page No 42: - Chapter 3 - Atoms & Molecules - Ncert Solutions class 9 - Science

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Question 1:

If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?

Answer:

One mole of carbon atoms weighs 12 g (Given)

i.e., mass of 1 mole of carbon atoms = 12 g

Then, mass of  number of carbon atoms = 12 g

Therefore, mass of 1 atom of carbon 

Question 2:

Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given, atomic mass of Na = 23 u, Fe = 56 u)?

Answer:

Atomic mass of Na = 23 u (Given)

Then, gram atomic mass of Na = 23 g

Now, 23 g of Na contains =   number of atoms

Thus, 100 g of Na contains   number of atoms

=   number of atoms

Again, atomic mass of Fe = 56 u(Given)

Then, gram atomic mass of Fe = 56 g

Now, 56 g of Fe contains =   number of atoms

Thus, 100 g of Fe contains   number of atoms

 number of atoms

Therefore, 100 grams of sodium contain more number of atoms than 100 grams of iron.