A sample of lithium sulfate, Li2SO4, 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
To determine the number of moles of Li+ ions in the given sample of lithium sulfate (Li2SO4), we need to consider the molar ratio between Li2SO4 and Li+ ions.
1) Moles of Li+ ions:
The formula of lithium sulfate (Li2SO4) indicates that for every 1 formula unit of Li2SO4, there are 2 moles of Li+ ions. Therefore, we can determine the number of moles of Li+ ions using the formula:
moles of Li+ ions = moles of Li2SO4 * (2 moles of Li+ ions / 1 mole of Li2SO4)
Given that the sample contains 6.78 x 10^23 formula units of Li2SO4, we can convert this to moles by dividing it by Avogadro's number (6.022 x 10^23) since 1 mole contains Avogadro's number of formula units. Then, we can use the above formula to calculate the moles of Li+ ions.
moles of Li+ ions = (6.78 x 10^23 formula units / 6.022 x 10^23 formula units/mol) * (2 moles of Li+ ions / 1 mole of Li2SO4)
2) Moles of ions:
To find the total moles of ions present in the sample of Li2SO4, we need to consider both Li+ ions and SO4^2- ions. The formula of lithium sulfate tells us that for every 1 formula unit of Li2SO4, there is 1 mole of Li+ ions and 1 mole of SO4^2- ions.
Therefore, the total moles of ions in the sample can be calculated as:
moles of ions = moles of Li2SO4 * (1 mole of Li+ ions + 1 mole of SO4^2- ions)
Now you can substitute the value for moles of Li2SO4 (which was calculated in step 1) in the equation above to find the moles of ions.
Please note that by calculating the moles of Li+ ions in question a, we have already found half of the answer to b as well, since the remaining half consists of the moles of SO4^2- ions.