Calculate The Percentage Composition of The Following Compounds Lithium Bromide
'/%3E%3Ccircle cx='48' cy='39' r='19' fill='%23f2c9a5'/%3E%3Cpath d='M27 35c3-16 39-17 42 2-8-8-27-9-42-2z' fill='%23374151'/%3E%3Cpath d='M21 86c5-24 49-28 56 0z' fill='%232563eb'/%3E%3Ccircle cx='41' cy='41' r='2' fill='%23111827'/%3E%3Ccircle cx='55' cy='41' r='2' fill='%23111827'/%3E%3Cpath d='M42 52c4 3 9 3 13 0' stroke='%2392400e' stroke-width='3' fill='none' stroke-linecap='round'/%3E%3C/svg%3E)
Reviewed by Calculator Editorial Team
Lithium bromide (LiBr) is an inorganic compound commonly used in absorption refrigeration systems and as a desiccant. Calculating its percentage composition helps understand its molecular makeup and properties. This guide explains how to determine the percentage composition of lithium bromide using atomic masses and the formula for percentage composition.
Introduction
The percentage composition of a compound shows the proportion of each element in the compound by mass. For lithium bromide (LiBr), we calculate the percentage of lithium and bromine in the compound.
Key points about lithium bromide:
- Chemical formula: LiBr
- Atomic mass of lithium (Li): 6.94 g/mol
- Atomic mass of bromine (Br): 79.90 g/mol
- Molar mass of LiBr: 6.94 + 79.90 = 86.84 g/mol
Formula for Percentage Composition
The percentage composition of an element in a compound is calculated using the formula:
Percentage Composition Formula
(Mass of element in 1 mole of compound / Molar mass of compound) × 100%
For lithium bromide:
- Percentage of lithium = (Mass of Li / Molar mass of LiBr) × 100%
- Percentage of bromine = (Mass of Br / Molar mass of LiBr) × 100%
Worked Example
Let's calculate the percentage composition of lithium bromide using the atomic masses:
Example Calculation
Given:
- Mass of lithium (Li) = 6.94 g/mol
- Mass of bromine (Br) = 79.90 g/mol
- Molar mass of LiBr = 6.94 + 79.90 = 86.84 g/mol
Percentage of lithium:
(6.94 / 86.84) × 100% ≈ 8.00%
Percentage of bromine:
(79.90 / 86.84) × 100% ≈ 92.00%
The results show that lithium makes up approximately 8.00% and bromine makes up approximately 92.00% of the mass of lithium bromide.
Interpreting Results
The percentage composition of lithium bromide reveals:
- The compound is primarily composed of bromine, which accounts for most of its mass.
- Lithium is present in smaller quantities, contributing to the compound's chemical properties.
- The percentages should sum to approximately 100%, accounting for rounding in the atomic masses.
Note
Small discrepancies in the sum of percentages are normal due to rounding atomic masses to two decimal places.
Frequently Asked Questions
What is the percentage composition of lithium bromide?
Lithium bromide (LiBr) has a percentage composition of approximately 8.00% lithium and 92.00% bromine.
How do you calculate the percentage composition of a compound?
Use the formula: (Mass of element in 1 mole of compound / Molar mass of compound) × 100%.
Why is bromine the majority element in lithium bromide?
Bromine has a much higher atomic mass (79.90 g/mol) compared to lithium (6.94 g/mol), making it the dominant element by mass.
Can the percentage composition of lithium bromide vary?
No, the percentage composition is fixed based on the atomic masses of lithium and bromine.