I cant answer that if I cant see it
I'm going to do it by stoichiometry :
molar mass of CH4 is 16
and there are 4 H atoms in each CH4 so one mole CH4 consists of 4 x 6.022x10^23 H atoms
so :
4gr CH4 x (1mole CH4 /16 gr CH4) x (4 x 6.022 x 10^23 H atoms/1mole CH4) =
=6.022 x 10^23 H atoms
Answer: The number of 'entities' in a mole of any pure substance is always that. 1 mole is equivalent to the number of atoms in a 12g lump of Carbon12.
Edit: I deliberately avoided using Avogadro's number as that is different, in a technical sense, to a mole. A mole is a base unit of the International System of Units (SI) which recognized amount of substance as an independent dimension of measurement. With this recognition, the Avogadro constant was no longer a pure number but a physical quantity associated with a unit of measurement, the reciprocal mole (mol−1) in SI units.
Therefore Avogadro constant is DERIVED from the mole (nowadays) to give something like 6.02214179 x 10^23 mole^(-1). (based on 2006 evidence)
<u>Given:</u>
Concentration of Na₂S = 0.765 M
Volume of Na₂S solution = 25.0 ml = 0.025 L
Final total volume = 225 ml = 0.225 L
<u>To determine:</u>
The concentration of Na+ ions
<u>Explanation:</u>
# moles of Na₂S = 0.765 * 0.025 = 0.0191 moles
Based on the atomic stoichiometry of Na₂S-
# moles of Na⁺ ions = 2*0.0191 = 0.0382 moles
conc of Na⁺ ions = 0.0382 moles/ 0.225 L = 0.169 M
Ans: [Na⁺] = 0.169 M
