How many O atoms are there in 1.51×10^23 molecules of trifluoroacetic acid, C2HF3O2?

9.033 × 10²³ molec C₂HF₃O₂ x (2 O atoms / 1 molec C₂HF₃O₂) = 1.8066 x 10²⁴ O atoms

The volume of the solvent used is less than 2 liters.

Explanation:

(MV) before dilution = (MV) after dilution.

M before dilution = 10.0 M, V before dilution = ??? L.

M after dilution = 1.0 M, V after dilution = 2.0 L.

∴ V before dilution = (MV) after dilution / (M) before dilution = (1.0 M)(2.0 L)/(10.0 M) = 0.2 L = 200.0 mL.

So, to prepare the diluted solution; we use 200 mL (0.2 L) from the stock solution (10.0 M NaCl) and add 1.8 L of the solvent (water).

Thus, the right choice is: The volume of the solvent used is less than 2 liters.