Answer: Molar mass of water is 18.016 g/mol.
Molar Mass of Water
The chemical formula of water is H2O. The molar mass of water is calculated by adding the molar masses of its constituent atoms—hydrogen (H) and oxygen (O).
In this guide, we will walk through the steps involved in calculating the molar mass of water and its importance in chemistry.
Understanding Molar Mass
The molar mass of a substance is the mass of one mole of its molecules, expressed in grams per mole (g/mol). A mole is a fundamental unit in chemistry that represents a large number of particles—specifically, Avogadro’s number, which is approximately \(6.022 \times 10^{23}\) particles per mole. For molecular compounds like water, the molar mass is calculated by adding up the molar masses of the atoms in the molecule.
The molar mass of each element can be found on the periodic table, expressed in grams per mole. In the case of water, we need to account for both the molar mass of hydrogen and the molar mass of oxygen to calculate the overall molar mass of a water molecule.
Molar Masses of Hydrogen and Oxygen
To calculate the molar mass of water, we need to know the molar masses of its components:
- Hydrogen (H): The molar mass of hydrogen is approximately 1.008 g/mol.
- Oxygen (O): The molar mass of oxygen is approximately 16.00 g/mol.
Water (H2O) consists of two hydrogen atoms and one oxygen atom, so we will use these values in our calculation of the total molar mass.
Formula for Calculating Molar Mass
The molar mass of a compound can be calculated using the following formula:
\[ \text{Molar Mass of Compound} = \sum (\text{Number of Atoms} \times \text{Molar Mass of Element}) \]
For water (H2O), the molar mass formula is:
\[ \text{Molar Mass of H}_2\text{O} = (2 \times \text{Molar Mass of H}) + (1 \times \text{Molar Mass of O}) \]
Step-by-Step Calculation
Let’s now calculate the molar mass of water by following these steps:
Step 1: Multiply the molar mass of hydrogen (H) by the number of hydrogen atoms in a water molecule. Since there are two hydrogen atoms, the calculation is:
\[ 2 \times 1.008 \, \text{g/mol} = 2.016 \, \text{g/mol} \]
Step 2: Multiply the molar mass of oxygen (O) by the number of oxygen atoms in a water molecule. Since there is one oxygen atom, the calculation is:
\[ 1 \times 16.00 \, \text{g/mol} = 16.00 \, \text{g/mol} \]
Step 3: Add the molar masses from steps 1 and 2 to find the total molar mass of water:
\[ \text{Molar Mass of H}_2\text{O} = 2.016 \, \text{g/mol} + 16.00 \, \text{g/mol} \]
\[ \text{Molar Mass of H}_2\text{O} = 18.016 \, \text{g/mol} \]
Final Molar Mass of Water
The molar mass of water (H2O) is approximately 18.016 g/mol. This means that one mole of water molecules weighs 18.016 grams. Understanding the molar mass of water is crucial in many chemical calculations, such as determining how much water is involved in a reaction or how many molecules are present in a given mass of water.
Conclusion
The molar mass of water (H2O) is approximately 18.016 g/mol, which is calculated by summing the molar masses of hydrogen and oxygen.