Lithium reacts spontaneously with bromine to produce lithium bromide. Write the balanced chemica

Lithium reacts spontaneously with bromine to produce lithium...

Key Concepts

Limiting Reactant

The limiting reactant in a chemical reaction is the reactant that is entirely consumed first, thereby stopping the reaction from proceeding further. Identifying the limiting reactant is essential because it determines the maximum amount of product that can be formed from a given set of reactants.

Mass-to-Mole Conversions

Mass-to-mole conversions involve using the molar mass of a substance to convert between the mass of a sample and the number of moles it contains. This conversion is a key step in stoichiometric calculations, allowing comparisons with the mole ratios given in the balanced chemical equation.

Excess Reactant

The excess reactant is the reactant that remains unreacted once the limiting reactant is completely consumed. Calculating the amount of excess reactant left after the reaction helps in understanding the efficiency of the reaction and in planning for the recovery or further use of the remaining substances.

Balanced Chemical Equation

The balanced chemical equation represents the conservation of atoms during a chemical reaction. For any reaction, it is crucial to ensure that the number of atoms for each element on the reactant side equals the number on the product side. This provides the foundation for all stoichiometric calculations, as it specifies the exact proportions by which substances react.

Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It allows you to predict the amounts of products formed or the reactants required by using the coefficients from a balanced chemical equation. This concept is essential for solving problems involving mass-to-mole conversions and to determine reactant-product ratios.

Transcript

00:01 For this question, we need to write down the balanced chemical equation for the reaction between lithium and bromine.

00:20 This reaction produces lithium bromide.

00:27 To balance the equation, we need to write a coefficient of 2 in front of lithium bromide to balance bromine, and then a tool to rebalance lithium.

00:40 And this is their balanced chemical equation for this reaction.

00:44 Having done that, we now have to determine the limiting reactant, that's question a, if we mix 25 grams of lithium with 25 grams of bromine.

01:04 In order to determine which one is a limiting reagent, we need to establish the theoretical ratio between lithium and bromine.

01:12 The theoretical more ratio is two moles to one mole.

01:19 However, the experimental mass, the experimental amount of substance is given in mass in grams, okay? so we better do the experimental, the theoretical ratio in terms of mass.

01:44 Okay, we want to do a theoretical mass ratio.

01:49 For that, we want to convert the moles, the theoretical moles, or the stereochometric moles, into mass.

01:56 Two moles of lithium must be multiplied by the atomic weight of lithium, which is 6 .94 grams per mole, and therefore, two moles of lithium is equivalent to 13 .88 grams.

02:25 Do the same thing with bromine.

02:27 We want to convert the mold of bromine to mass grams of bromine.

02:34 This is lithium.

02:37 So we multiply one mole times two times the atomic weight of bromine, which is 79 .90 grams per mole.

03:00 Moles cancel.

03:02 And then we have 79 .9 .2 multiplied by 2, multiplied by 1 is 159 .80 grams of bromine.

03:18 Now we established the theoretical ratio, which is two moles of lithium to one more of bromine.

03:30 But in terms of mass, it would be 13 .88 grams of lithium react with 159 .80 grams of bromine.

03:49 And this ratio equals to 0 .0869.

04:04 Now we calculate the experimental ratio, which is the ratio by which the ratio of the between the amount of lithium and bromine that are mixed together in the experiment.

04:22 So we have 25 grams of lithium, divided by 25 grams of bromine.

04:33 What we get is a ratio of 1...

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