A scientist wants to determine how many moles of bromine $(Br_2)$ are needed to make 8.33 mol of lithium bromide (LiBr).
$2 Li+Br_2 \rightarrow 2 LiBr$
How many moles of bromine are needed?
Answer (1)
Determine the mole ratio between B r 2 and L i B r from the balanced equation.
Set up a proportion to relate the moles of B r 2 to the moles of L i B r .
Solve for the unknown number of moles of B r 2 .
Calculate the moles of bromine needed: 4.165 .
Explanation
Understanding the Problem We are given the balanced chemical equation: 2 L i + B r 2 → 2 L i B r . This tells us that 2 moles of lithium (Li) react with 1 mole of bromine ( B r 2 ) to produce 2 moles of lithium bromide (LiBr). We want to find out how many moles of B r 2 are needed to produce 8.33 moles of LiBr.
Mole Ratio From the balanced equation, we can see that the mole ratio between B r 2 and L i B r is 1:2. This means that for every 2 moles of L i B r produced, we need 1 mole of B r 2 .
Setting up the Proportion To find the number of moles of B r 2 needed to produce 8.33 moles of L i B r , we can set up a proportion: m o l ese wl in eo f e wl in e L i B r m o l ese wl in eo f e wl in e B r 2 = 2 1 Let x be the number of moles of B r 2 needed. Then: 8.33 x = 2 1 To solve for x , we multiply both sides of the equation by 8.33: x = 2 8.33
Calculating the Moles of Bromine Now, we perform the calculation: x = 2 8.33 = 4.165 So, we need 4.165 moles of B r 2 to produce 8.33 moles of L i B r .
Final Answer Therefore, the number of moles of bromine needed is 4.165.
Examples
In chemical synthesis, understanding stoichiometry is crucial for calculating the required amounts of reactants to produce a desired amount of product. For instance, if a chemist aims to synthesize 8.33 moles of lithium bromide (LiBr) in a lab, they need to determine the precise amount of bromine ( B r 2 ) required. By using the balanced chemical equation and mole ratios, they can accurately calculate that 4.165 moles of B r 2 are needed. This ensures efficient use of resources and minimizes waste, which is vital for both economic and environmental reasons.
