Formula Mass and Molar Mass of a Compound

Summary

This video explains how to calculate the formula mass and molar mass of ammonium nitrate (NH4NO3). It walks through the process of adding the atomic masses of nitrogen, hydrogen, and oxygen from the periodic table, considering the number of atoms for each element. The total formula mass is calculated as 80.5 AMU, and this is converted to molar mass, which is also 80.5 grams per mole. The video then demonstrates how to use this information to convert between grams and moles of ammonium nitrate using a simple conversion factor.

Takeaways

• 🔢 Formula mass is calculated by adding up the atomic masses of all the atoms in a compound.
• 🧪 The example compound discussed is ammonium nitrate (NH4NO3).
• 🔬 To find the formula mass of ammonium nitrate, you must sum the atomic masses of nitrogen, hydrogen, and oxygen.
• 🟡 Nitrogen has an atomic mass of 14.01 AMU, and there are two nitrogen atoms in NH4NO3.
• ⚫ Hydrogen has an atomic mass of 1.008 AMU, and there are four hydrogen atoms in NH4NO3.
• 🟠 Oxygen has an atomic mass of 16.00 AMU, and there are three oxygen atoms in NH4NO3.
• 📊 The total formula mass of ammonium nitrate adds up to 80.5 AMU.
• ⚖️ The formula mass in AMU is numerically equal to the molar mass in grams per mole (G/mol).
• 🧮 The molar mass of ammonium nitrate is 80.5 G/mol, which helps in conversion calculations.
• 📏 By using the molar mass, one can convert between grams of a substance and moles, as shown in the example where 10 grams of ammonium nitrate equals 0.125 moles.

Q & A

What is the formula mass of ammonium nitrate?

The formula mass of ammonium nitrate (NH4NO3) is 80.5 AMU.

How do you calculate the formula mass of ammonium nitrate?

To calculate the formula mass of ammonium nitrate, add the atomic masses of all the atoms in the compound: 2 nitrogens (14.01 AMU each), 4 hydrogens (1.008 AMU each), and 3 oxygens (16.00 AMU each).

Where do the atomic masses of elements come from?

The atomic masses of elements come from the periodic table.

What is the molar mass of ammonium nitrate?

The molar mass of ammonium nitrate is 80.5 grams per mole (g/mol).

How is the molar mass related to the formula mass?

The molar mass is numerically equal to the formula mass, but the units are different: formula mass is in AMU and molar mass is in grams per mole (g/mol).

Why is molar mass useful in chemical calculations?

Molar mass is useful because it can be used in conversion factors to relate mass (in grams) to the number of moles of a substance.

How would you calculate the number of moles from a given mass of ammonium nitrate?

To calculate the number of moles from a given mass, divide the mass of ammonium nitrate by its molar mass. For example, 10.0 g of ammonium nitrate divided by 80.5 g/mol gives 0.125 moles.

What is the significance of ensuring units cancel in conversions?

Ensuring units cancel in conversions is important to make sure the calculation is set up correctly, allowing the result to be in the desired units, such as moles.

What is the difference between formula mass and molecular mass?

Formula mass refers to both ionic and molecular compounds, while molecular mass specifically refers to molecular compounds (not ionic).

Can the terms molecular weight and molecular mass be used interchangeably?

Yes, molecular weight and molecular mass are often used interchangeably, though they specifically refer to molecular compounds.