- What is the molar mass of copper sulfate pentahydrate (CuSO4·5H2O) ? (From now on, we will call this copper sulfate rather than copper sulfate pentahydrate.)
- What is the molar mass of Na2CO3 ?
The Correct Answer and Explanation is :
1. Molar mass of Copper Sulfate (CuSO₄·5H₂O):
To find the molar mass of copper sulfate (CuSO₄·5H₂O), we add up the atomic masses of each component in the formula:
- Copper (Cu): 63.55 g/mol
- Sulfur (S): 32.07 g/mol
- Oxygen (O) in sulfate (SO₄): 16.00 g/mol × 4 = 64.00 g/mol
- Water (H₂O): 18.015 g/mol × 5 = 90.075 g/mol (for the 5 molecules of water)
Now, adding them all together:
[
63.55 \, \text{g/mol} \, (\text{Cu}) + 32.07 \, \text{g/mol} \, (\text{S}) + 64.00 \, \text{g/mol} \, (\text{O in SO₄}) + 90.075 \, \text{g/mol} \, (\text{H₂O}) = 249.695 \, \text{g/mol}
]
Thus, the molar mass of copper sulfate (CuSO₄·5H₂O) is 249.7 g/mol.
2. Molar Mass of Sodium Carbonate (Na₂CO₃):
Now, let’s find the molar mass of sodium carbonate (Na₂CO₃). We will follow a similar method of summing the atomic masses of all elements in the compound:
- Sodium (Na): 22.99 g/mol × 2 = 45.98 g/mol
- Carbon (C): 12.01 g/mol
- Oxygen (O): 16.00 g/mol × 3 = 48.00 g/mol
Now, adding them all together:
[
45.98 \, \text{g/mol} \, (\text{Na}) + 12.01 \, \text{g/mol} \, (\text{C}) + 48.00 \, \text{g/mol} \, (\text{O}) = 105.99 \, \text{g/mol}
]
Thus, the molar mass of sodium carbonate (Na₂CO₃) is 106.0 g/mol.
Explanation:
The molar mass is the mass of one mole of a substance and is calculated by adding the atomic masses of the elements present in the formula of the compound, taking into account the number of atoms or molecules of each element.
For copper sulfate (CuSO₄·5H₂O), the formula contains copper, sulfur, oxygen, and water molecules. The atomic masses are obtained from the periodic table, and the formula’s subscripts indicate how many atoms of each element to consider.
Similarly, in sodium carbonate (Na₂CO₃), the formula tells us that there are 2 sodium atoms, 1 carbon atom, and 3 oxygen atoms, so we multiply the atomic masses of each element by the number of atoms and add them up to find the total molar mass.
These calculations are important in chemistry because they help to determine the quantities of substances involved in reactions, allowing for precise measurements and predictions.