To find the mass concentration of the original H2O2 solution, we need to calculate the number of moles of H2O2 in the diluted solution and then convert it to mass.
First, let's calculate the number of moles of H2O2 in the diluted solution:
Volume of H2O2 solution = 2.500 mL = 0.002500 L
Concentration of H2O2 in diluted solution = 3% w/v = 3 g/100 mL = 30 g/L
Number of moles of H2O2 in diluted solution = Concentration x Volume
= 30 g/L x 0.002500 L
= 0.075 mol
Next, let's calculate the number of moles of H2O2 in the 0.02000 mol/L solution:
Volume of 0.02000 mol/L solution = 40.05 mL = 0.04005 L
Number of moles of H2O2 in 0.02000 mol/L solution = Concentration x Volume
= 0.02000 mol/L x 0.04005 L
= 0.000802 mol
Since the number of moles of H2O2 in the diluted solution and the 0.02000 mol/L solution are equal (they completely react with each other), we can set up the following equation:
Number of moles of H2O2 in diluted solution = Number of moles of H2O2 in 0.02000 mol/L solution
0.075 mol = 0.000802 mol
Now, let's find the volume of the original (undiluted) H2O2 solution:
Volume of the original (undiluted) H2O2 solution = Volume of diluted solution / Dilution factor
= 25.00 mL / (25.00 mL / 2.500 mL)
= 2.500 mL
Finally, let's calculate the mass concentration of the original H2O2 solution:
Mass of H2O2 in original solution = Number of moles x Molar mass
= 0.075 mol x 34.02 g/mol (molar mass of H2O2)
= 2.5525 g
Mass concentration of the original H2O2 solution = Mass of H2O2 / Volume of original solution
= 2.5525 g / 2.500 mL
= 1.021 g/mL
Therefore, the mass concentration of the original (undiluted) H2O2 solution is 1.021 g/mL.
2.500 mL of ~3% w/v (i.e. 3 g in 100. mL) H2O2 solution is diluted with water to 25.00mL. If 40.05 mL of 0.02000 mol/L solution is required to completely react with 25.00 mL of diluted H2O2 solution, what is the mass concentration of the original (undiluted) H2O2 solution?
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