Answer to Question #170268 in General Chemistry for Violet

Question

Which sample contains the same number of atoms as 24 grams of carbon? (1) 10. g Ne (2) 24g Mg (3) 80. g Ar (4) 4.0 g He (Can you explain or write it out please)

Answer 1

M(C) = 12 g mol^-1;

M(Ne) = 20 g mol^-1;

M(Mg) = 24 g mol^-1;

M(Ar) = 40 g mol^-1;

M(He) = 4 g mol^-1.

Solution:

One mole of any substance contains 6.022×10²³ atoms/molecules (N_a).

Hence,

Number of atoms in 24 g of C = (24 g / 12 g mol^-1) × N_a = 2.0 × N_a atoms

(1): Number of atoms in 10 g of Ne = (10 g / 20 g mol^-1) × N_a = 0.5 × N_a atoms

(2): Number of atoms in 24 g of Mg = (24 g / 24 g mol^-1) × N_a = 1.0 × N_a atoms

(3): Number of atoms in 80 g of Ar = (80 g / 40 g mol^-1) × N_a = 2.0 × N_a atoms

(4): Number of atoms in 4 g of He = (4 g / 4 g mol^-1) × N_a = 1.0 × N_a atoms

Hence, (3) (80 grams of argon) contains same number of atoms (2N_a atoms) as in 24 grams of carbon.

Answer: 80 grams of argon (Ar) contains same number of atoms (2.0 × N_a atoms) as in 24 grams of carbon (C).