Calculate the molecular mass of ammonia, NH$$_3$$​, using the provided atomic masses (Atomic mass of N = 14u and H = 1u ).

Correct option is D

The correct answer is (d) 17 u

Explanation:

To calculate the molecular mass of ammonia (NH₃), we need to sum the atomic masses of its constituent atoms:

• The molecular formula of ammonia is NH₃, which means it consists of 1 nitrogen (N) atom and 3 hydrogen (H) atoms.
• Atomic mass of nitrogen (N) = 14 u
• Atomic mass of hydrogen (H) = 1 u

Now, the molecular mass of NH₃ is calculated as follows:

​$$\text{Molecular Mass of NH₃} = (\text{Atomic Mass of N}) + 3 \times (\text{Atomic Mass of H})$$​​

​$$\text{Molecular Mass of NH₃} = 14 \, \text{u} + 3 \times 1 \, \text{u}$$​​

​$$\text{Molecular Mass of NH₃} = 14 \, \text{u} + 3 \, \text{u} = 17 \, \text{u}$$​

Thus, the molecular mass of ammonia is 17 u.

Information Booster:

Atomic Mass:

• Definition: The mass of a single atom, typically measured in atomic mass units (amu or u).
• Unit: Atomic mass unit (amu or u).
• Example: The atomic mass of carbon (C) is approximately 12 amu, which corresponds to the combined mass of protons and neutrons in the nucleus of a carbon atom.
• Significance: It reflects the number of protons and neutrons in an atom.

Molecular Mass:

• Definition: The sum of the atomic masses of all atoms in a molecule.
• Unit: Atomic mass units (amu or u).
• Example: The molecular mass of water (H₂O) is calculated as 2 × 1 (for two hydrogen atoms) + 16 (for one oxygen atom), which gives a molecular mass of 18 amu.
• Significance: It is used to determine the mass of a molecule, which can be helpful in stoichiometric calculations.

Key Difference:

• Atomic Mass refers to the mass of a single atom, while Molecular Mass refers to the total mass of a molecule, which consists of two or more atoms.

Molar Mass:

• Definition: The mass of one mole (6.022 × 10²³ particles) of a substance, expressed in grams per mole (g/mol).
• Unit: Grams per mole (g/mol).
• Relation: Molar mass is numerically equal to the atomic or molecular mass but in units of grams per mole.
• Example: The molar mass of carbon (C) is 12 g/mol. For water (H₂O), it is 18 g/mol (2 × 1 + 16).
• Significance: It is used to convert between the mass of a substance and the amount of substance (in moles).