Find the molar masses of the following compounds:




1. LiI
2. PbCO4
3. Mg(OH)2
4. (NH4)3PO4

Find the percent composition (percent by mass) of the given element in the following compounds:


1. Fluorine in AgF
2. Hydrogen in glucose (C6H12O6)
3. Oxygen in Fe2(SO4)3
PART II: CONVERTING BETWEEN GRAMS AND MOLES
Use molar mass as the conversion factor to convert between grams and moles. Remember, in order to go from grams→moles, you divide by the molar mass. In order to go from moles→grams, you multiply by the molar mass.

1. Convert 250 grams of K3PO4 to moles
2. 2 moles of Na3P to grams
3. 95 grams of NaCl to moles
PART III: MOLARITY AND MOLALITY



Type I (Basic Molarity Calculations)
1. 2 moles of NaCl are added to make 230. mL of a solution. What is the molarity of the solution?

2. A solution contains 2.1 moles of HCl and has a molarity of 6.00 M. What volume does the solution occupy?

Type II (Given Grams and Volume, Solving for Molarity):
3. What is the molarity of a solution prepared with 250 grams of KCl and 250 mL of water?

4. What is the molarity of a 3.0 L of solution with 39g of Al(OH)3?

Type III (Given Volume and Molarity, Asked to Solve for Grams):

5. How many grams of LiBr are needed to prepare 3 liters of 3.5M solution?

6. How many grams of CaSO4 are needed to prepare 10.5 L of 3M solution?

everything

To find the molar masses of compounds, you need to determine the atomic mass of each element in the compound and add them together according to their respective stoichiometric ratios.

1. LiI:
- Li has an atomic mass of approximately 6.94 g/mol.
- I has an atomic mass of approximately 126.9 g/mol.
The molar mass of LiI is 6.94 g/mol + 126.9 g/mol = 133.84 g/mol.

2. PbCO4:
- Pb has an atomic mass of approximately 207.2 g/mol.
- C has an atomic mass of approximately 12.01 g/mol.
- O has an atomic mass of approximately 16.00 g/mol.
The molar mass of PbCO4 is 207.2 g/mol + 12.01 g/mol + 16.00 g/mol (4 oxygen atoms) = 375.22 g/mol.

3. Mg(OH)2:
- Mg has an atomic mass of approximately 24.31 g/mol.
- O has an atomic mass of approximately 16.00 g/mol.
- H has an atomic mass of approximately 1.01 g/mol.
The molar mass of Mg(OH)2 is 24.31 g/mol + 16.00 g/mol (2 oxygen atoms) + 1.01 g/mol (2 hydrogen atoms) = 58.33 g/mol.

4. (NH4)3PO4:
- N has an atomic mass of approximately 14.01 g/mol.
- H has an atomic mass of approximately 1.01 g/mol.
- P has an atomic mass of approximately 30.97 g/mol.
- O has an atomic mass of approximately 16.00 g/mol.
The molar mass of (NH4)3PO4 is 14.01 g/mol (3 nitrogen atoms) + 1.01 g/mol (12 hydrogen atoms) + 30.97 g/mol + 16.00 g/mol (4 oxygen atoms) = 149.09 g/mol.

Now let's find the percent composition of elements in compounds:

1. Fluorine in AgF:
The molar mass of AgF is 107.87 g/mol.
Ag has an atomic mass of approximately 107.87 g/mol.
F has an atomic mass of approximately 18.998 g/mol.
Percent composition of F in AgF = (18.998 g/mol / 107.87 g/mol) * 100% = 17.62%.

2. Hydrogen in glucose (C6H12O6):
The molar mass of C6H12O6 is 180.16 g/mol.
C has an atomic mass of approximately 12.01 g/mol.
H has an atomic mass of approximately 1.01 g/mol.
O has an atomic mass of approximately 16.00 g/mol.
Percent composition of H in C6H12O6 = (12.01 g/mol (12 hydrogen atoms) / 180.16 g/mol) * 100% = 6.67%.

3. Oxygen in Fe2(SO4)3:
The molar mass of Fe2(SO4)3 is 399.88 g/mol.
Fe has an atomic mass of approximately 55.85 g/mol.
S has an atomic mass of approximately 32.07 g/mol.
O has an atomic mass of approximately 16.00 g/mol.
Percent composition of O in Fe2(SO4)3 = (16.00 g/mol (12 oxygen atoms) / 399.88 g/mol) * 100% = 48.04%.

To convert grams to moles or moles to grams, you need to use the molar mass as a conversion factor. Divide the given mass by the molar mass to convert from grams to moles, and multiply the given moles by the molar mass to convert from moles to grams.

1. Convert 250 grams of K3PO4 to moles:
The molar mass of K3PO4 is 212.27 g/mol.
Moles = grams / molar mass = 250 g / 212.27 g/mol ≈ 1.18 moles.

2. 2 moles of Na3P to grams:
The molar mass of Na3P is 163.97 g/mol.
Grams = moles * molar mass = 2 moles * 163.97 g/mol = 327.94 grams.

3. 95 grams of NaCl to moles:
The molar mass of NaCl is 58.44 g/mol.
Moles = grams / molar mass = 95 g / 58.44 g/mol ≈ 1.63 moles.

Now let's move on to molarity and molality calculations:

1. 2 moles of NaCl are added to make 230 mL of a solution. What is the molarity of the solution?
Molarity (M) = moles of solute / liters of solution.
Liters of solution = mL of solution / 1000 = 230 mL / 1000 = 0.23 L.
Molarity = 2 moles / 0.23 L ≈ 8.70 M.

2. A solution contains 2.1 moles of HCl and has a molarity of 6.00 M. What volume does the solution occupy?
Volume = moles of solute / molarity.
Volume = 2.1 moles / 6.00 M ≈ 0.35 L or 350 mL.

3. What is the molarity of a solution prepared with 250 grams of KCl and 250 mL of water?
First, convert grams of KCl to moles using the molar mass:
Molar mass of KCl is 74.55 g/mol.
Moles of KCl = 250 g / 74.55 g/mol ≈ 3.36 moles.
Then calculate the total volume of the solution:
Total volume = mL of KCl + mL of water = 250 mL + 250 mL = 500 mL = 0.5 L.
Molarity = moles of solute / liters of solution = 3.36 moles / 0.5 L = 6.72 M.

4. What is the molarity of a 3.0 L solution with 39 g of Al(OH)3?
First, convert grams of Al(OH)3 to moles using the molar mass:
Molar mass of Al(OH)3 is 78.00 g/mol.
Moles of Al(OH)3 = 39 g / 78.00 g/mol = 0.50 moles.
Molarity = moles of solute / liters of solution = 0.50 moles / 3.0 L ≈ 0.17 M.

Now let's solve for grams in molarity calculations:

5. How many grams of LiBr are needed to prepare 3 liters of 3.5 M solution?
Moles of LiBr = molarity * liters of solution = 3.5 M * 3 L = 10.5 moles.
Molar mass of LiBr is 86.85 g/mol.
Grams = moles * molar mass = 10.5 moles * 86.85 g/mol = 912.83 grams.

6. How many grams of CaSO4 are needed to prepare 10.5 L of 3 M solution?
Moles of CaSO4 = molarity * liters of solution = 3 M * 10.5 L = 31.5 moles.
Molar mass of CaSO4 is 136.14 g/mol.
Grams = moles * molar mass = 31.5 moles * 136.14 g/mol = 4286.71 grams.

A lot of work here. I don't want to just give you the answers but I'll be happy to help you through them. Exactly what do you not understand?