Lead(II) nitrate and aluminum chloride react according to...

Lead(II) nitrate and aluminum chloride react according to the following equation: $3 \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}+2 \mathrm{AlCl}_{3} \longrightarrow 3 \mathrm{PbCl}_{2}+2 \mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}$ In an experiment, 8.00 g of lead nitrate reacted with $2.67 \mathrm{g}$ of aluminum chloride to give $5.55 \mathrm{g}$ of lead chloride. (a) Which reactant was the limiting reagent? (b) What was the percent yield?

Lead(II) nitrate and aluminum chloride react according to the following equation: $3 \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}+2 \mathrm{AlCl}_{3} \longrightarrow 3 \mathrm{PbCl}_{2}+2 \mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}$ In an experiment, 8.00 g of lead nitrate reacted with $2.67 \mathrm{g}$ of aluminum chloride to give $5.55 \mathrm{g}$ of lead chloride.
(a) Which reactant was the limiting reagent?
(b) What was the percent yield?

Key Concepts

Percent Yield

Percent yield is a measure of the efficiency of a chemical reaction, calculated by comparing the actual yield obtained from an experiment to the theoretical yield predicted by stoichiometric calculations. It is expressed as a percentage and provides insight into the practical aspects of the reaction, such as side reactions or incomplete conversions.

Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It involves calculations based on the molar ratios derived from the balanced chemical equation, allowing one to determine how much of each substance is needed or produced in a reaction.

Limiting Reagent Analysis

Limiting reagent analysis is the process of determining which reactant will be completely used up first in a chemical reaction, thereby limiting the amount of product that can be formed. By comparing the mole ratios of the available reactants to the stoichiometric ratios required by the balanced equation, one can identify the reactant that restricts the reaction’s progress.

Transcript

00:01 So this question gives us this reaction between lead nitrate and aluminum chloride and tells us that 8 grams of lead nitrate is reacting with 2 .67 grams of aluminum chloride, and this reaction is giving an actual yield of 5 .5 grams of lead chloride, and it wants us to determine what is the limiting reagent and what is the percent yield.

00:28 So first we need to determine which is the limiting reagent, and we can't do this unless we have the molecular weights for the compounds of interest.

00:40 And that is lead nitrate and our aluminum chloride.

00:44 So we can calculate that quickly by summing the weights of each atom which make up the compound.

00:51 And we'll find that the molecular weight of lead nitrate is 331 .2.

00:58 Grams per mole and the weight of lead chloride is 133 .33 grams per mole and because we'll need it later we'll also just calculate the weight of lead chloride and that is 278 .1 grams per mole.

01:18 So now we can determine what is limiting.

01:27 So first let's see how many mole of lead nitrogen.

01:34 Rate is in 8 grams of it.

01:38 And we can do this by referencing our conversion triangle, which gives us the relationship between the mass of a compound in grams, the number of moles within that particular weight of compound, and the molecular weight of that compound.

01:57 And this conversion triangle tells us that to find the number of moles, we can divide the weight by the molecular weight.

02:05 And we we can do that for lead nitrate and divide its weight in grams by the molecular weight of lead nitrate.

02:15 And we'll find that 8 grams of lead nitrate contains 0 .0 to 42 moles of lead nitrate.

02:28 And we can do the same for aluminum chloride.

02:35 So we will divide the weight of aluminum chloride in grams by the molecular weight of aluminum chloride in grams per mole.

02:52 And we'll find that 2 .67 grams of aluminum chloride contains 0 .02 mole of aluminum chloride.

03:05 But this doesn't really tell us which is limiting.

03:08 What we have to do is compare how many of...

03:13 One compound is necessary to completely react with the other.

03:18 So let's just choose from let's just choose from aluminum chloride and we want to know how many mole of lead nitrate.

03:37 How many mole of lead nitrate is required to react completely with our zero 0 .02 mole of aluminum chloride.

03:54 And we can do this by multiplying our number of mole of aluminum chloride by the conversion, which we can get that ratio from our balanced chemical equation...

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