A sample of lithium sulfate, LiSO4, contains 6.78 x 10^23 formula units.
a) How many moles of Li+ ions are there in the sample?
b) How many moles of ions are there in the sample?
My work:
I think a) is 2.26 moles
And b i am not sure
Hey, Li has ONE valence electron
I think you mean Li2SO4
6.02 * 10^23 molecules/mol
so we have
6.78/6.02 = 1.13 mols of Li2SO4
which mean
2.26 mols of Li+ ions
then we have 1.13 mols of SO4-- ions
so
2.26 + 1.13 = 3.39 mols of ions in all
To find the number of moles of Li+ ions in the sample, we need to determine the ratio of Li+ ions to formula units in lithium sulfate (LiSO4). The chemical formula of lithium sulfate tells us that there is one Li+ ion for every LiSO4 formula unit. Therefore, the number of moles of Li+ ions in the sample can be calculated as follows:
Number of moles of Li+ ions = Number of formula units of LiSO4 × (1 mole of Li+ ions / 1 mole of LiSO4)
Given that the sample contains 6.78 x 10^23 formula units of LiSO4, we can substitute this value into the equation:
Number of moles of Li+ ions = 6.78 x 10^23 formula units × (1 mole of Li+ ions / 1 mole of LiSO4)
To find the molar ratio between Li+ ions and LiSO4, we need to determine the molar mass of LiSO4. The molar mass of Li is approximately 6.94 g/mol, the molar mass of S is approximately 32.07 g/mol, and the molar mass of O is approximately 16.00 g/mol. Adding these values gives us the molar mass of LiSO4:
Molar mass of LiSO4 = (6.94 g/mol × 1) + (32.07 g/mol × 1) + (16.00 g/mol × 4) = 109.94 g/mol
Now we can use the molar mass of LiSO4 to convert the number of formula units to moles:
Number of moles of Li+ ions = 6.78 x 10^23 formula units × (1 mole of Li+ ions / 1.09 x 10^2 g of LiSO4) × (1.09 x 10^2 g of LiSO4 / 1 mole of LiSO4)
Evaluating this expression, we find:
Number of moles of Li+ ions = 6.78 x 10^23 / 1.09 x 10^2 = 6.21 x 10^21 moles
Therefore, the number of moles of Li+ ions in the sample is approximately 6.21 x 10^21 moles.
Now let's move on to part b) to find the number of moles of ions in the sample.
For lithium sulfate (LiSO4), there is one Li+ ion and one SO4^2- ion per formula unit. Therefore, the total number of moles of ions in the sample can be calculated as:
Number of moles of ions = Number of formula units of LiSO4 × (2 moles of ions / 1 mole of LiSO4)
Using the given value of 6.78 x 10^23 formula units, we can substitute it into the equation:
Number of moles of ions = 6.78 x 10^23 formula units × (2 moles of ions / 1 mole of LiSO4)
Following the same steps as before, we can use the molar mass of LiSO4 to convert the number of formula units to moles:
Number of moles of ions = 6.78 x 10^23 formula units × (2 moles of ions / 1.09 x 10^2 g of LiSO4) × (1.09 x 10^2 g of LiSO4 / 1 mole of LiSO4)
Evaluating this expression, we find:
Number of moles of ions = 1.24 x 10^22 moles
Therefore, the number of moles of ions in the sample is approximately 1.24 x 10^22 moles.
In summary:
a) The number of moles of Li+ ions in the sample is approximately 6.21 x 10^21 moles.
b) The number of moles of ions in the sample is approximately 1.24 x 10^22 moles.