Commercial breathalyzers contain .75 mg of K2Cr2O7, 1.5 mL of H20 and 1.5 mL of H2SO4. What is the concentraion of the dichromate in the solution?(hint:the acid is a solvent)
Concn in what units?
moles/L??
0.75 mg = 0.00075 g and moles = grams/molar mass.
Then M = moles/L soln and th volume is 3.0 mL or 0.003 L.
If you want it in mg/L. it is 0.75 mg/0.003 L = ??
To find the concentration of dichromate (K2Cr2O7) in the solution, we need to first calculate the number of moles of K2Cr2O7.
The molar mass of K2Cr2O7 is:
2 mol of K (potassium) = 2 * 39.10 g/mol = 78.20 g/mol
2 mol of Cr (chromium) = 2 * 52.00 g/mol = 104.00 g/mol
7 mol of O (oxygen) = 7 * 16.00 g/mol = 112.00 g/mol
Total molar mass of K2Cr2O7 = 78.20 + 104.00 + 112.00 = 294.20 g/mol
The amount of K2Cr2O7 in the solution is given as 0.75 mg. To convert this to grams, we divide by 1000:
0.75 mg = 0.75 / 1000 = 0.00075 g
Now, we can calculate the number of moles of K2Cr2O7 using the formula:
moles = mass / molar mass
moles of K2Cr2O7 = 0.00075 g / 294.20 g/mol = 2.55 x 10^-6 mol
Next, we need to find the total volume of the solution. The solution contains 1.5 mL of H2O and 1.5 mL of H2SO4. As mentioned in the hint, the H2SO4 acts as a solvent, so the total volume is equal to the volume of H2SO4, which is 1.5 mL.
Finally, we can calculate the concentration of the dichromate in the solution using the formula:
concentration (in mol/L) = moles / volume (in L)
concentration = 2.55 x 10^-6 mol / 0.0015 L = 1.70 x 10^-3 mol/L
Therefore, the concentration of dichromate in the solution is 1.70 x 10^-3 mol/L.