9. Which sample contains a mole of atoms?

A) 23 g Na

B) 24 g C

C) 42 g Kr

D) 78 g K

Answer: option A. 23g Na

Explanation:

To know which of the options are correct, let's solve each of the options

A. Mass of Na = 23g

MM of Na = 23g/mol.

n = Mass / Molar Mass

n = 23/23 = 1mole

B. Mass of carbon = 24g

MM of carbon = 12g/mol

n = Mass / Molar Mass

n = 24/12 = 2mole

C. Mass of Kr = 42g

MM of Kr = 84g/mol

n = Mass / Molar Mass

n = 42/84 = 0.5mole

D. Mass of K = 78g

MM of K = 39g/mol

n = Mass / Molar Mass

n = 78/39 = 2mole.

From the above illustration, only 23g of Na contains a mole of the atom