What is the molar mass of water (H2O)?

Analysis

To find the molar mass of a compound, we need to sum the atomic masses of all the individual atoms present in its chemical formula. The formula for water is H₂O.

Concept

The molar mass of a compound is calculated by:

1. Identifying the number of atoms of each element in the formula.
2. Multiplying the number of atoms by their respective relative atomic masses (found on the Periodic Table).
3. Adding these values together.

Key Atomic Masses:

• Hydrogen (H) = 1 g/mol
• Oxygen (O) = 16 g/mol

Step-by-Step Solution

1. Break down the formula: H₂O consists of 2 atoms of Hydrogen and 1 atom of Oxygen.
2. Calculate the contribution of each element: • Hydrogen: $2 \text{ atoms} \times 1 \text{ g/mol} = 2 \text{ g/mol}$ • Oxygen: $1 \text{ atom} \times 16 \text{ g/mol} = 16 \text{ g/mol}$
3. Sum the values: • Total Molar Mass = $2 \text{ g/mol} + 16 \text{ g/mol} = 18 \text{ g/mol}$

Conclusion

Exam Tip

Always keep a mental note of the atomic masses of the first 20 elements in the Periodic Table (H, He, Li, Be, B, C, N, O, F, Ne, etc.). Knowing these by heart will save you precious time during your JAMB exam, as you won't have to constantly flip to the periodic table provided in the booklet!