At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO 3 : 2 KClO 3 (s) → 2 KCl(s) + 3 O 2 (g) ΔH = -89.4 kJ For this reaction, calculate H for the formation of (b) 10.4 g of KCl.

hey everyone in this example, we have the following reaction And we need to find the entropy of formation of 5.15 g of lead chloride. So we want to recognize whether our equation is balanced and based on our psyche aama tree and the coefficients. It's definitely a balanced equation. Our next step is to recognize that we are given the entropy of formation for reaction for our formation of lead chloride as negative 3 36 point okay, joules per mole and this is for one mole of our lead chloride. So we want to recognize that that comes from the coefficient one which is in front of our product lead chloride. So our next step is to first because we are given the amount in grams for lead chloride. We need to convert from grams to moles. So we want to start from 5.15 g of our lead chloride. And then we're going to go from grams to moles by recalling our molar mass for the compound. So when we find lead in group four a on our periodic tables, we see that it has a molar mass of 207.2 g per mole. And when we find chlorine in group seven a on the periodic table, We see that it has a molar mass of 35.4, 5 g per mole. Now recognize that in our formula, we have two moles of our Chlorine Atom. And so we're going to multiply this by two. So to get the total mass for the compound lead chloride, we're going to have these two masses added up together And we're going to have a total of 278.1 g per mole for our compound P BCL two. So we're going to plug that in. So we have to 78.1 g for one mole of our lead chloride. So this allows us to cancel out our units of grams leaving us with moles, which is what we want. And we're going to get a value equal to 0.01815 moles of our lead chloride. And actually I re I just need to rewrite this number. So it's actually 0.018 519 moles of our lead chloride. And so now we can calculate our anthem P A formation for our lead chloride For our 5.15 g of lead chloride. And we would get that that is equal to our entropy of formation for one mole, which is given as negative 3 36.0 Killer Jewels for one mole of lead chloride. And then we're multiplying this by our molds of our 5.15 g of our lead chloride which we found above. So we plugged that in as 0. moles of our lead chloride. So this allows us to cancel out most, leaving us with kayla jewels as our final unit, Which is definitely what we need for entropy of formation. And we get a value in our calculators equal to negative 6.22238. So we can round this to about 366 so that we have negative 6.22 kg joules as our final answer For the entropy of formation of our 5. g of our product, lead chloride. So I hope that everything we reviewed was clear. If you have any questions, please leave them down below and I will see everyone in the next practice video.

Ch.5 - Thermochemistry

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Brown 14th Edition

Ch.5 - Thermochemistry

Problem 46b

Chapter 5, Problem 46b

At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO₃: 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g) ΔH = -89.4 kJ For this reaction, calculate H for the formation of (b) 10.4 g of KCl.

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Identify the molar mass of KCl by adding the atomic masses of K (potassium) and Cl (chlorine).

Calculate the number of moles of KCl in 10.4 g using the formula: \( \text{moles of KCl} = \frac{\text{mass of KCl}}{\text{molar mass of KCl}} \).

Use the stoichiometry of the balanced chemical equation to determine the relationship between moles of KCl and the enthalpy change (\( \Delta H \)).

Calculate the enthalpy change for the formation of the calculated moles of KCl using the relationship: \( \Delta H = \text{moles of KCl} \times \frac{-89.4 \text{ kJ}}{2 \text{ moles of KCl}} \).

Express the final enthalpy change in kJ for the formation of 10.4 g of KCl.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced equation. It allows us to determine the relationships between the amounts of substances involved in a reaction, such as how many grams of a product can be formed from a given mass of reactants. In this case, stoichiometry will help us relate the mass of KCl produced to the amount of KClO3 reacted.

Enthalpy Change (ΔH)

Enthalpy change (ΔH) is a measure of the heat energy absorbed or released during a chemical reaction at constant pressure. In the given reaction, ΔH = -89.4 kJ indicates that the reaction is exothermic, meaning it releases energy. Understanding ΔH is crucial for calculating the energy associated with the formation of products, such as KCl, from the reactants.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is essential for converting between the mass of a substance and the number of moles, which is necessary for stoichiometric calculations. To find the amount of KCl formed, we need to know its molar mass to convert the given mass (10.4 g) into moles for further calculations.

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Textbook Question

Consider the following reaction: 2 CH₃OH(g) → 2 CH₄(g) + O₂(g) ΔH = +252.8 kJ (d) How many kilojoules of heat are released when 38.5 g of CH₄(g) reacts completely with O₂(g) to form CH₃OH(g) at constant pressure?

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Textbook Question

When solutions containing silver ions and chloride ions are mixed, silver chloride precipitates Ag⁺(aq) + Cl^-(aq) → AgCl(s) H = -65.5 kJ (a) Calculate H for the production of 0.450 mol of AgCl by this reaction. (b) Calculate H for the production of 9.00 g of AgCl. (c) Calculate H when 9.25⨉10^-4 mol of AgCl dissolves in water.

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Textbook Question

At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO₃: 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g) ΔH = -89.4 kJ For this reaction, calculate H for the formation of (a) 1.36 mol of O₂

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Textbook Question

At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO₃: 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g) ΔH = -89.4 kJ (c) The decomposition of KClO₃ proceeds spontaneously when it is heated. Do you think that the reverse reaction, the formation of KClO₃ from KCl and O₂, is likely to be feasible under ordinary conditions? Explain your answer.

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Textbook Question

Consider the combustion of liquid methanol, CH₃OH(l): CH₃OH(l) + 3/2 O₂(g) → CO₂(g) + 2 H₂O(l) ΔH = -726.5 kJ (a) What is the enthalpy change for the reverse reaction?

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Textbook Question

Consider the combustion of liquid methanol, CH₃OH(l): CH₃OH(l) + 3/2 O₂(g) → CO₂(g) + 2 H₂O(l) ΔH = -726.5 kJ (b) Balance the forward reaction with whole-number coefficients. What is ΔH for the reaction represented by this equation?

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At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO3: 2 KClO3(s) → 2 KCl(s) + 3 O2(g) ΔH = -89.4 kJ For this reaction, calculate H for the formation of (b) 10.4 g of KCl.

Verified video answer for a similar problem:

Key Concepts

Stoichiometry

Enthalpy Change (ΔH)

Molar Mass

At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO₃: 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g) ΔH = -89.4 kJ For this reaction, calculate H for the formation of (b) 10.4 g of KCl.