Consider the following five samples of substances: A. 88 g of CO_2...

Molar mass of $\mathrm{CO}_2 = 12 + 2 \times 16 = 44 \text{ g/mol}$
Moles of $\mathrm{CO}_2 = \dfrac{88}{44} = 2 \text{ moles}$
Total atoms in A $= 2 \times 3 \times N_A = 6 N_A$

Molar mass of $\mathrm{O}_2 = 2 \times 16 = 32 \text{ g/mol}$
Moles of $\mathrm{O}_2 = \dfrac{96}{32} = 3 \text{ moles}$
Total atoms in B $= 3 \times 2 \times N_A = 6 N_A$

Molar mass of $\mathrm{NH}_3 = 14 + 3 \times 1 = 17 \text{ g/mol}$
Moles of $\mathrm{NH}_3 = \dfrac{34}{17} = 2 \text{ moles}$
Total atoms in C $= 2 \times 4 \times N_A = 8 N_A$

Molar mass of $\mathrm{H}_2\mathrm{O} = 2 \times 1 + 16 = 18 \text{ g/mol}$
Moles of $\mathrm{H}_2\mathrm{O} = \dfrac{36}{18} = 2 \text{ moles}$
Total atoms in D $= 2 \times 3 \times N_A = 6 N_A$

Molar mass of $\mathrm{Ne} = 20 \text{ g/mol}$
Moles of $\mathrm{Ne} = \dfrac{40}{20} = 2 \text{ moles}$
Total atoms in E $= 2 \times 1 \times N_A = 2 N_A$

Samples A, B, and D contain an identical total number of atoms ($6 N_A$).

Answer: A, B and D only