b. How many moles of hydrogen and oxygen atoms are present in 1 mol H2O?
c. What are the masses of hydrogen and oxygen in 1.0 mol H2O?
d. What is the mass of 1.0 mol H2O?
T he Correct Answer and Explanation is :
Answers:
b. In 1 mole of H₂O, there are:
- 2 moles of hydrogen atoms, because each water molecule (H₂O) has two hydrogen atoms.
- 1 mole of oxygen atoms, because each water molecule contains one oxygen atom.
c. To calculate the masses of hydrogen and oxygen in 1.0 mol of H₂O:
- Hydrogen:
Each mole of hydrogen atoms has a molar mass of approximately 1.008 g/mol.
Since there are 2 moles of hydrogen atoms in 1 mole of H₂O:
2×1.008 g=2.016 g2 \times 1.008 \, \text{g} = 2.016 \, \text{g} - Oxygen:
The molar mass of oxygen is approximately 16.00 g/mol.
So, 1 mole of oxygen atoms = 16.00 g
d. The total mass of 1.0 mol of H₂O is the sum of the masses of hydrogen and oxygen: 2.016 g (H)+16.00 g (O)=18.016 g2.016 \, \text{g (H)} + 16.00 \, \text{g (O)} = \boxed{18.016 \, \text{g}}
Explanation :
Water (H₂O) is a simple molecule composed of two hydrogen atoms and one oxygen atom. When discussing amounts in chemistry, the mole is a fundamental unit used to measure the number of atoms, molecules, or ions in a substance. One mole corresponds to Avogadro’s number, approximately 6.022×10236.022 \times 10^{23} particles.
In 1 mole of water, every individual molecule contains 2 hydrogen atoms and 1 oxygen atom. Therefore, 1 mole of water molecules contains 2 moles of hydrogen atoms and 1 mole of oxygen atoms. This proportional relationship is important for understanding chemical reactions and stoichiometry.
To determine the mass of hydrogen and oxygen in water, we use the atomic masses from the periodic table. Hydrogen has a molar mass of about 1.008 g/mol, and oxygen has a molar mass of about 16.00 g/mol. Since there are two hydrogen atoms in each molecule, the total mass of hydrogen in 1 mole of water is 2×1.008=2.016 g2 \times 1.008 = 2.016 \, \text{g}. The oxygen, being one atom per water molecule, contributes 16.00 g.
Adding these together gives the total mass of one mole of water as 18.016 g. This value is crucial in laboratory calculations, allowing chemists to weigh out exact amounts of water or calculate yields in reactions involving water.
Understanding the composition of water at the molecular level helps explain its physical and chemical properties, such as boiling point, polarity, and its role as a universal solvent. Mastery of mole concepts is essential for accurate quantitative analysis in chemistry.
