Okay I've got a HUGE chem test tomorrow and I desperately need help! Please help!!!!
73. Hematite (Fe2O3) and magnetite (Fe3O4) are two ores used as sources of iron. Which ore provides the greatest percentage of iron per kilogram?
78. A hydrate contains .050 mole of H2O to every .00998 mole of ionic compound XYY the formula of the hydrate XY.
79. Calculate the mass of the water of hydration if a hydrate looses .025 mole of H2O when heated.
I absolutely have no idea how to start any of these, please help!
73. Because this is chemistry you're intimidated. % anything = (mass of that/total mass)*100
%Fe in Fe2O3 = (2*atomic mass Fe/molar mass Fe2O3)*100 = ?
Works the same way for Fe3O4.
78. Sorry, I don't understand this one. Neither XYY nor XY makes sense to me. Read that sentence; something seems to be missiing. My guess; however, is that you want to know the formula of the hydrate and that is 1 mol compound:Y mols H2O. To get that 0.05mols/0.00998 - 5.01 mols H2O which rounds to 5.0. So the formula is, for example, CuSO4.5H2O which is in the ration of 1 mol salt to 5 mol H2O.
79.
So it loses 0.025 mols H2O. Convert that to grams H2O. g = mols x molar mass = ?
Sure, I can help you with these chemistry questions. Let's take them one by one:
Q73: To determine which ore provides the greatest percentage of iron per kilogram, we need to calculate the molar masses of hematite (Fe2O3) and magnetite (Fe3O4). The molar mass of an element or compound is the sum of the atomic masses of its constituent atoms.
1. Hematite (Fe2O3):
- The atomic mass of Fe (iron) is 55.845 g/mol.
- The atomic mass of O (oxygen) is 16.00 g/mol.
So, the molar mass of Fe2O3 can be calculated as:
2 * (55.845 g/mol) + 3 * (16.00 g/mol) = 159.69 g/mol.
2. Magnetite (Fe3O4):
- The atomic mass of Fe (iron) is 55.845 g/mol.
- The atomic mass of O (oxygen) is 16.00 g/mol.
So, the molar mass of Fe3O4 can be calculated as:
3 * (55.845 g/mol) + 4 * (16.00 g/mol) = 231.53 g/mol.
Now, to determine the percentage of iron in each ore, we need to compare the molar mass of iron to the total molar mass of the respective compound.
1. Hematite (Fe2O3):
- The molar mass of Fe in Fe2O3 is 2 * (55.845 g/mol) = 111.69 g/mol.
- The total molar mass of Fe2O3 is 159.69 g/mol.
To find the percentage of iron in hematite, we can use the following formula:
(111.69 g/mol / 159.69 g/mol) * 100%
2. Magnetite (Fe3O4):
- The molar mass of Fe in Fe3O4 is 3 * (55.845 g/mol) = 167.54 g/mol.
- The total molar mass of Fe3O4 is 231.53 g/mol.
To find the percentage of iron in magnetite, we can use the following formula:
(167.54 g/mol / 231.53 g/mol) * 100%
Comparing the two percentages, we can determine which ore provides the greatest percentage of iron per kilogram.
Q78: In this question, we need to find the formula of the hydrate XY. We are given that the hydrate contains 0.050 mole of H2O for every 0.00998 mole of ionic compound XYY.
To find the formula, we need to simplify the mole ratios. In this case, the mole ratio of H2O to XYY is 0.050 / 0.00998, which can be simplified further if needed.
Q79: In this question, we need to calculate the mass of water lost when a hydrate loses 0.025 mole of H2O.
First, we need to determine the molar mass of H2O, which is 18.015 g/mol (2 * 1.008 g/mol for hydrogen + 16.00 g/mol for oxygen).
Then, we can use the molar mass of water and the number of moles lost to calculate the mass of water lost:
0.025 mol * 18.015 g/mol
I hope this helps you understand how to approach these questions. If you have any further questions, feel free to ask!