How to find moles given oxidation numbers and chemical formula?
Trying to do my chemistry lab but i'm super duper stuck. please help me i'm gonna die. this is the part i'm stuck on:
The overall charge on the complex, [Ni(en)(H2O)]^2+ * SO4^2- * H2O is zero; the charge on sulfate ion is 2-;en and water ligands both have a charge of zero; and nickel has a charge of 2+. Using this information and your previous experimental results, calculate the number of moles of SO4^2- in 100 grams of your complex and the mass percent of SO4^2- in your complex.
previous experimental results:
Molarity of Ni^2+ in unknown sample: 0.0647M
Moles of Ni^2+ in 100 g of complex: 0.475 moles
Mass % of Ni^2+ in complex: 27.86%
From your formula there is 1 mol Ni in 1 mol of the complex AND 1 mol SO4; therefore, mols Ni from your experimental result in 100 g of complex = mols SO4^2- in 100 g commplex. Right?
And if mass %Ni is 27.86 then mass %SO4^2- is 27.86 x (molar mass SO4/atomic mass Ni) = ?
thanks for answering! when we found the moles of en (ethylenediamine) in a previous step, it wasn't a 1 to 1 mole ratio with Ni, it was .283 moles in 100g of complex. i think we're supposed to use the oxidation numbers along with the moles of nickel to find the moles of SO4, but i'm not sure how to do that
To find the number of moles of SO4^2- in 100 grams of the complex and the mass percent of SO4^2- in the complex, you can follow these steps:
Step 1: Determine the molar mass of the complex [Ni(en)(H2O)]^2+.
- Note the symbols and subscripts in the chemical formula: Ni(en)(H2O)
- Using the periodic table, find the molar masses of each element: Ni = 58.69 g/mol, en = 48.08 g/mol, H2O = 18.02 g/mol
- Calculate the molar mass of the complex by adding the molar masses of each component: Molar mass = (58.69 g/mol) + (48.08 g/mol) + (18.02 g/mol) = 124.79 g/mol
Step 2: Calculate the number of moles of Ni^2+ in the complex.
- Given: Moles of Ni^2+ in 100 g of complex = 0.475 moles
- This means that for every 100 grams of the complex, there are 0.475 moles of Ni^2+.
Step 3: Calculate the mass of the complex [Ni(en)(H2O)]^2+ in 100 grams.
- Use the molar mass calculated in Step 1 and the moles of Ni^2+ from Step 2 to find the mass of the complex: Mass of complex = (Molar mass) * (Moles of Ni^2+)
- Mass of complex = (124.79 g/mol) * (0.475 moles) = 59.28225 grams
Step 4: Determine the mass of SO4^2- in the complex.
- Since the overall charge on the complex is zero, the sum of all the charges on the ligands and ions should also be zero.
- The charge on [Ni(en)(H2O)]^2+ is 2+, and the charge on SO4^2- is 2-. Therefore, the charges balance each other out.
- This means that there is one SO4^2- ion for each [Ni(en)(H2O)]^2+ ion in the complex.
- Since the moles of Ni^2+ in the complex is known to be 0.475 moles, the moles of SO4^2- is also 0.475 moles.
Step 5: Calculate the number of moles of SO4^2- in 100 grams of the complex.
- Given: Moles of SO4^2- = 0.475 moles
- This means that for every 100 grams of the complex, there are 0.475 moles of SO4^2-.
Step 6: Calculate the mass percent of SO4^2- in the complex.
- Mass percent = (Mass of SO4^2- / Mass of complex) x 100%
- Given: Mass of SO4^2- = 0.475 moles x 96.06 g/mol (molar mass of SO4^2-) = 45.6635 grams
- Mass of complex = 59.28225 grams (calculated in Step 3)
- Mass percent = (45.6635 grams / 59.28225 grams) x 100% = 77.11%
Therefore, the number of moles of SO4^2- in 100 grams of the complex is 0.475 moles, and the mass percent of SO4^2- in the complex is 77.11%.
To find the number of moles of SO4^2- in 100 grams of the complex, you need to use the given information and apply the concept of stoichiometry.
1. Start by converting the mass percent of Ni^2+ in the complex to the mass of Ni^2+ in 100 grams of the complex. Since the mass percent of Ni^2+ in the complex is 27.86%, you can calculate the mass of Ni^2+ as follows:
Mass of Ni^2+ = (27.86/100) * 100 grams = 27.86 grams
2. Use the molar mass of Ni^2+ (which you can find on the periodic table) to convert the mass of Ni^2+ to moles. The molar mass of Ni^2+ is 58.69 g/mol.
Moles of Ni^2+ = Mass of Ni^2+ / Molar mass of Ni^2+ = 27.86 grams / 58.69 g/mol = 0.4748 moles
3. Use the molarity of Ni^2+ in the unknown sample to find the volume of the sample required to obtain 0.475 moles of Ni^2+. The equation to use is:
Moles = Molarity * Volume
Rearrange the equation to solve for volume:
Volume = Moles / Molarity = 0.475 moles / 0.0647 M = 7.34 liters (rounding to 3 decimal places)
4. Convert the volume of the sample from liters to milliliters by multiplying by 1000. This is necessary because 1 liter is equal to 1000 milliliters.
Volume = 7.34 liters * 1000 = 7340 milliliters
5. Based on the given information, the complex contains [Ni(en)(H2O)]^2+ * SO4^2- * H2O. The charge of the complex is zero, so the sum of the charges on all individual ions must be zero. The charge on the nickel ion (Ni^2+) is 2+, and both the en ligand and water ligands have a charge of zero. Therefore, the total charge contributed by the SO4^2- ion must be 2- to balance the charge.
6. Since the charge on the SO4^2- ion is 2-, the number of moles of SO4^2- in the complex is equal to the number of moles of Ni^2+ in the complex. Therefore, the number of moles of SO4^2- in 100 grams of the complex is also 0.4748 moles.
To calculate the mass percent of SO4^2- in the complex, use the formula:
Mass percent of SO4^2- = (mass of SO4^2- / mass of the complex) * 100%
Since you have already calculated the moles of SO4^2- and the molar mass of SO4^2-, you can calculate the mass of SO4^2- as follows:
Mass of SO4^2- = Moles of SO4^2- * Molar mass of SO4^2- = 0.4748 moles * (32.06 g/mol + 4 * 16.00 g/mol) = 22.25 grams (rounded to 2 decimal places)
Finally, calculate the mass percent of SO4^2-:
Mass percent of SO4^2- = (22.25 grams / 100 grams) * 100% = 22.25%
Therefore, there are 0.4748 moles of SO4^2- in 100 grams of the complex, and the mass percent of SO4^2- in the complex is approximately 22.25%.