My prelab is telling me to find the initial concentrations of I(^-) and S208(^2-) given the following reaction:
25 mL of 0.2 M KI + 48.00 mL 0.2 M KNO3 + 1 mL 0.4 M Na2S2O3 + 1 mL starch + 25 mL 0.2 M (NH4)2S2O8 + 1 drop EDTA
How do I calculate the concentration of I^-1 when I am given the molality of KI? Is the molality of I^-1 a percentage of this number of the total? Same goes for S2O8(^-2) in (NH4)2S2O8.
Thanks!!
Didn't I answer this earlier?
You have 0.2M KI and it has been diluted. So the initial concn is
0.2 x [(25 mL/(25 + 48+1+1+25)]
You have 0.4M Na2S2O3 so the initial concn is (before any reaction) is
0.4 x (1 mL/total ML)
To calculate the initial concentration of I^- and S2O8(2-) in the given reaction, you need to convert the given molality of KI and (NH4)2S2O8 to molarity.
Molality (m) is defined as the amount of solute (in moles) dissolved per kilogram of solvent. Molarity (M), on the other hand, is the amount of solute (in moles) dissolved per liter of solution.
To convert molality to molarity, you need to know the density of the solution. Once you have the density, you can use the following formula:
Molarity (M) = (Molality (m) × Density of the solution) / Molar Mass of the solute
Let's calculate the initial concentration of I^- and S2O8(2-) using this formula:
1. For I^-:
- Given: Molality of KI = 0.2 M
- Convert the given molality to molarity using the density of the KI solution.
- Assume the density of the KI solution is 1 g/mL (you can check the density value on the bottle if provided).
- The molar mass of KI is 166 g/mol.
- Calculate the molarity of I^- in KI using the formula:
Molarity (I^-) = (Molality (KI) × Density (KI)) / Molar Mass (KI)
Molarity (I^-) = (0.2 M × 1 g/mL) / 166 g/mol
2. For S2O8(2-):
- Given: Molality of (NH4)2S2O8 = 0.2 M
- Convert the given molality to molarity using the density of the (NH4)2S2O8 solution.
- Assume the density of the (NH4)2S2O8 solution is 1 g/mL.
- The molar mass of (NH4)2S2O8 is 228 g/mol.
- Calculate the molarity of S2O8(2-) in (NH4)2S2O8 using the formula:
Molarity (S2O8(2-)) = (Molality ((NH4)2S2O8) × Density ((NH4)2S2O8)) / Molar Mass ((NH4)2S2O8)
Molarity (S2O8(2-)) = (0.2 M × 1 g/mL) / 228 g/mol
By plugging in the values (density=1 g/mL and molar mass values), you can calculate the molarities of I^- and S2O8(2-) in the given reaction. Remember to include proper units in your final answers.
Note: If the density of the solution is provided in a different unit (e.g., g/cm^3), make sure to convert it to g/mL before using it in the calculations.