Answer
A molecule's molecular weight, also known as its molecular mass or molar mass, is determined by summing the atomic masses of all the atoms in the molecule. The molecular weight is typically expressed in atomic mass units (amu) or unified atomic mass units (u), and it provides a quantitative measure of the mass of a molecule.
Here's how you can determine the molecular weight of a molecule:
1. **Determine the Chemical Formula**: Start by identifying the chemical formula of the molecule. The chemical formula tells you the types and numbers of atoms present in the molecule.
2. **Look Up Atomic Masses**: Each element has a standard atomic mass listed on the periodic table. These atomic masses are typically expressed in atomic mass units (amu) or unified atomic mass units (u).
3. **Count the Atoms**: Count the number of each type of atom in the molecule based on the chemical formula. For example, if you have the molecule H2O (water), there are two hydrogen atoms (H) and one oxygen atom (O).
4. **Multiply and Sum**: Multiply the number of each type of atom by its atomic mass and then sum these products to calculate the molecular weight. The formula for calculating the molecular weight (MW) is as follows:
MW = (Number of H atoms × Atomic mass of H) + (Number of O atoms × Atomic mass of O)
For water (H2O):
MW = (2 × 1.008 u) + (1 × 15.999 u) = 2.016 u + 15.999 u = 18.015 u
So, the molecular weight of water (H2O) is approximately 18.015 atomic mass units (u).
It's important to note that molecular weights can be calculated not only for simple molecules like H2O but also for complex molecules like proteins, DNA, or organic compounds with numerous atoms. In these cases, you would follow the same principles: count the atoms of each element in the chemical formula and sum their individual atomic masses.
Molecular weight is a valuable parameter in various fields of science, including chemistry, biochemistry, and pharmacology. It is used for a wide range of applications, such as determining the stoichiometry of chemical reactions, calculating concentrations of solutions, and understanding the properties and behaviors of molecules in chemical and biological systems.
Work Step by Step
A molecule's molecular weight, also known as its molecular mass or molar mass, is determined by summing the atomic masses of all the atoms in the molecule. The molecular weight is typically expressed in atomic mass units (amu) or unified atomic mass units (u), and it provides a quantitative measure of the mass of a molecule.
Here's how you can determine the molecular weight of a molecule:
1. **Determine the Chemical Formula**: Start by identifying the chemical formula of the molecule. The chemical formula tells you the types and numbers of atoms present in the molecule.
2. **Look Up Atomic Masses**: Each element has a standard atomic mass listed on the periodic table. These atomic masses are typically expressed in atomic mass units (amu) or unified atomic mass units (u).
3. **Count the Atoms**: Count the number of each type of atom in the molecule based on the chemical formula. For example, if you have the molecule H2O (water), there are two hydrogen atoms (H) and one oxygen atom (O).
4. **Multiply and Sum**: Multiply the number of each type of atom by its atomic mass and then sum these products to calculate the molecular weight. The formula for calculating the molecular weight (MW) is as follows:
MW = (Number of H atoms × Atomic mass of H) + (Number of O atoms × Atomic mass of O)
For water (H2O):
MW = (2 × 1.008 u) + (1 × 15.999 u) = 2.016 u + 15.999 u = 18.015 u
So, the molecular weight of water (H2O) is approximately 18.015 atomic mass units (u).
It's important to note that molecular weights can be calculated not only for simple molecules like H2O but also for complex molecules like proteins, DNA, or organic compounds with numerous atoms. In these cases, you would follow the same principles: count the atoms of each element in the chemical formula and sum their individual atomic masses.
Molecular weight is a valuable parameter in various fields of science, including chemistry, biochemistry, and pharmacology. It is used for a wide range of applications, such as determining the stoichiometry of chemical reactions, calculating concentrations of solutions, and understanding the properties and behaviors of molecules in chemical and biological systems.
