A sample of sodium carbonate, Na2CO3, weighs 44.0 g. Calculate the number of Na2CO3 formula units, the number of Na+ ions, and moles of CO3
2− ions
44.0 g/gram formula mass = ?
There are twice the number of Na^+ per 1 formula unit and the same number of mols [CO3]^2-
To calculate the number of Na2CO3 formula units, you need to convert the given sample weight of 44.0 g to moles.
First, find the molar mass of Na2CO3:
Na: 23.0 g/mol
C: 12.0 g/mol
O: 16.0 g/mol
Molar mass of Na2CO3 = 2(23.0 g/mol) + 12.0 g/mol + 3(16.0 g/mol) = 106.0 g/mol
Now, calculate the number of moles:
moles = mass / molar mass
moles = 44.0 g / 106.0 g/mol ≈ 0.4151 mol
Since 1 mole of Na2CO3 contains 6.02 * 10^23 formula units (Avogadro's number), you can calculate the number of formula units:
number of formula units = moles * (6.02 * 10^23)
number of formula units = 0.4151 mol * (6.02 * 10^23) ≈ 2.5 * 10^23 formula units
Next, calculate the number of Na+ ions present in the given sample:
Each Na2CO3 formula unit contains 2 Na+ ions.
number of Na+ ions = number of formula units * 2
number of Na+ ions = 2.5 * 10^23 formula units * 2 ≈ 5.0 * 10^23 Na+ ions
Finally, calculate the moles of CO3 2- ions in the sample:
Each Na2CO3 formula unit contains 1 CO3 2- ion.
moles of CO3 2- ions = number of formula units * 1
moles of CO3 2- ions = 2.5 * 10^23 formula units * 1 ≈ 2.5 * 10^23 moles