A student investigating the properties of solutions containing carbonate ions prepared a solution containing 7.493 g Na2CO3 in a flask of volume 250 mL. Some of the solution was transferred to a buret. What volume of solution should be dispensed from the bret to provide 8.455 mmol Na2CO3? Answer in units of mL.
moles Na2CO3 = grams/molar mass
moles Na2CO3 - 7.493/105.99 = ??
(Na2CO3) = moles/L = ??moles/0.250 = x M.
moles = M x L OR
millimoles = M x mL.
You know millimoles and M, calculate mL.
To find the volume of solution that should be dispensed from the buret, we need to calculate the concentration (in moles per mL) of the Na2CO3 solution.
First, we need to convert the mass of Na2CO3 (7.493 g) into moles. To do this, we divide the mass by the molar mass of Na2CO3.
The molar mass of Na2CO3 is calculated as follows:
Na: 22.99 g/mol
C: 12.01 g/mol
O: 16.00 g/mol
Molar mass of Na2CO3 = (2 * 22.99) + 12.01 + (3 * 16.00) = 105.99 g/mol
Now, we can calculate the number of moles of Na2CO3:
moles = mass / molar mass = 7.493 g / 105.99 g/mol = 0.0706 mol
Next, we need to calculate the concentration of the Na2CO3 solution:
concentration (moles per mL) = moles / volume (in L) = 0.0706 mol / 0.250 L = 0.2824 mol/L
Now that we have the concentration of the solution, we can find the volume (in mL) needed to provide 8.455 mmol of Na2CO3.
First, convert 8.455 mmol to moles:
moles = 8.455 mmol / 1000 = 0.008455 mol
Next, use the concentration of the solution to find the volume:
volume (mL) = moles / concentration (mol/L) = 0.008455 mol / 0.2824 mol/L = 0.0299 L * 1000 = 29.9 mL
Therefore, the volume of solution that should be dispensed from the buret is 29.9 mL.