Find the mass in 2.6 mol of lithium bromide.
The correct answer and explanation is:
To find the mass of 2.6 moles of lithium bromide (LiBr), follow these steps:
- Calculate the molar mass of lithium bromide.
- Lithium (Li) has an atomic mass of approximately 6.94 grams per mole.
- Bromine (Br) has an atomic mass of approximately 79.90 grams per mole.
- Add these together to get the molar mass of LiBr:
6.94 g/mol + 79.90 g/mol = 86.84 g/mol.
- Use the formula:
Mass = Number of moles × Molar mass. - Substitute the known values:
Mass = 2.6 mol × 86.84 g/mol = 225.784 grams.
Therefore, the mass of 2.6 moles of lithium bromide is approximately 225.78 grams.
Explanation:
Molar mass is the mass of one mole of a substance, measured in grams per mole (g/mol). It is calculated by adding the atomic masses of all atoms in the chemical formula. Lithium bromide consists of one lithium atom and one bromine atom. The atomic masses of elements are found on the periodic table. Lithium’s atomic mass is about 6.94 g/mol, and bromine’s is about 79.90 g/mol.
When calculating the total mass of a given amount of substance, multiplying the number of moles by the molar mass gives the mass in grams. This approach works because one mole of lithium bromide weighs 86.84 grams. If you have 2.6 moles, you multiply 2.6 by the molar mass, resulting in the total mass.
This method applies to any compound or element when you need to convert between moles and mass. It is essential in chemistry for preparing solutions, reactions, and understanding the quantities of substances involved.
In this problem, the calculation was straightforward because lithium bromide contains only one lithium and one bromine atom. If the formula had more atoms, each element’s atomic mass would be multiplied by the number of atoms before adding together for the total molar mass.