A scientist wants to determine how many moles of chlorine ([tex]Cl_2[/tex]) are needed to make 116 g of lithium chloride (LiCl).
[tex]2 Li+Cl_2 \rightarrow 2 LiCl[/tex]
The molar mass of each substance is provided in the table below.
| Substance | Molar Mass (g/mol) |
| :-------- | :----------------- |
| Lithium (Li) | 6.97 |
| Chlorine ([tex]Cl_2[/tex]) | 70.90 |
| Lithium chloride (LiCl) | 42.42 |
How many moles of chlorine are needed?
Answer (1)
Calculate the number of moles of L i Cl produced: moles of L i Cl = 42.42 g/mol 116 g = 2.734559 mol .
Use the mole ratio from the balanced equation to find the moles of C l 2 needed: moles of C l 2 = 2 2.734559 mol = 1.3672795 mol .
Round the answer to three significant figures.
The number of moles of chlorine needed is 1.367 .
Explanation
Problem Analysis We are given the balanced chemical equation 2 L i + C l 2 i g ha rro w 2 L i Cl and asked to find how many moles of C l 2 are needed to produce 116 g of L i Cl . We are also given the molar masses of L i , C l 2 , and L i Cl .
Calculating Moles of LiCl First, we need to find the number of moles of L i Cl produced. We can use the formula: moles = molar mass mass moles of L i Cl = 42.42 g/mol 116 g = 2.734559 mol
Calculating Moles of Cl2 From the balanced chemical equation, we know that 1 mole of C l 2 produces 2 moles of L i Cl . Therefore, the mole ratio of C l 2 to L i Cl is 1:2. To find the number of moles of C l 2 needed, we divide the number of moles of L i Cl by 2: moles of C l 2 = 2 moles of L i Cl = 2 2.734559 mol = 1.3672795 mol
Final Answer Therefore, 1.367 moles of chlorine are needed to make 116 g of lithium chloride.
Examples
In industrial chemistry, calculating the required amount of reactants is crucial for efficient production. For example, if a factory wants to produce a certain amount of lithium chloride for batteries, they need to determine the exact amount of chlorine and lithium required. This calculation ensures that the reaction proceeds as expected, minimizing waste and maximizing the yield of the desired product. Accurate mole calculations are essential for cost-effective and sustainable chemical manufacturing.
