6 liters of 0.1 molar sodium hydroxide solution reacted with 2 liters of 0.1 molar iron(III) chloride solution. What is the molar concentration of sodium ions in the remaining solution? 1. 0.075 ( Correct Answer )
2. 0.15
3. 0.3
4. 0.6

The equivalent factor used to convert molecules of oxygen to moles of oxygen is Avogadro's number which is 6.022 x10^23. We divide the given number of molecules by Avogadro's number to get the number of moles. In this case,  4.28 * 10^19 molecules divided by 6.022 x10^23 is equal to 7.11 x10^-5 moles.