A mixture contains only NaCl and Fe(NO3). A 0.456g sample of the mixture is dissolved in water, and an excess of NaOH is added, producing a precipitate of Fe(OH)3. The precipitate is filtered, dried and weighed. Its mass is 0.107g. Calculate the following:
a. the mass of the iron in the sample
b. mass of Fe(NO)3.
How do I work out this question? Thank you.
for the mass of iron, take the percent composition of iron in iron hydroxide times the mass.
for the mass of feNO3, you have the mass of iron, use percentage composition agian to get the mass of the iron nitrate.
thank you so much for your help!
4555677777
To solve this question, you need to follow a step-by-step approach. Here's how you can work it out:
Step 1: Determine the moles of Fe(OH)3 precipitate
- Convert the mass of the precipitate (0.107g) to moles using the molar mass of Fe(OH)3. The molar mass of Fe(OH)3 is calculated as follows:
- Molar mass of Fe(OH)3 = (molar mass of Fe) + 3*(molar mass of O) + 3*(molar mass of H)
- Molar mass of Fe(OH)3 = (55.845 g/mol) + 3*(16.00 g/mol) + 3*(1.008 g/mol) = 106.867 g/mol
- The moles of Fe(OH)3 can be calculated using the formula:
- Moles = Mass / Molar mass
- Moles = 0.107g / 106.867 g/mol
Step 2: Determine the moles of Fe(NO3)3
- Since there is an excess of NaOH, the precipitation reaction can be written as:
Fe(NO3)3 + 3NaOH → Fe(OH)3 + 3NaNO3
- From the balanced equation, we know that one mole of Fe(NO3)3 produces one mole of Fe(OH)3.
- Therefore, the moles of Fe(NO3)3 is also equal to the moles of Fe(OH)3 determined in Step 1.
Step 3: Determine the mass of Fe(NO3)3
- The mass of Fe(NO3)3 can be calculated using the formula:
- Mass = Moles * Molar mass
- Mass = Moles * (molar mass of Fe(NO3)3)
- The molar mass of Fe(NO3)3 can be calculated as follows:
- Molar mass of Fe(NO3)3 = (molar mass of Fe) + 3*(molar mass of N) + 9*(molar mass of O)
- Molar mass of Fe(NO3)3 = (55.845 g/mol) + 3*(14.007 g/mol) + 9*(16.00 g/mol)
- Mass = Moles * (molar mass of Fe(NO3)3)
Step 4: Determine the mass of iron in the sample
- Since one mole of Fe(NO3)3 contains one mole of iron (Fe), the mass of iron can be calculated as follows:
- Mass of iron = Moles of Fe(NO3)3 * (molar mass of Fe)
- Mass of iron = Moles of Fe(NO3)3 * (55.845 g/mol)
By following these steps, you can determine the mass of iron in the sample (a) and the mass of Fe(NO3)3 (b).