Ch.4 - Chemical Quantities & Aqueous Reactions

Problem 36

Chapter 4, Problem 36

For each precipitation reaction, calculate how many grams of the first reactant are necessary to completely react with 55.8 g of the second reactant. a. 2 KI(aq) + Pb(NO3)2(aq) → PbI2(s) + 2 KNO3(aq) b. Na2CO3(aq) + CuCl2(aq) → CuCO3(s) + 2 NaCl(aq) c. K2SO4(aq) + Sr(NO3)2(aq) → SrSO4(s) + 2 KNO3(aq)

Verified step by step guidance

Identify the balanced chemical equation for each reaction to determine the stoichiometry between the reactants.

Calculate the molar mass of the second reactant (55.8 g) for each reaction.

Convert the mass of the second reactant to moles using its molar mass.

Use the stoichiometry from the balanced equation to find the moles of the first reactant needed to completely react with the moles of the second reactant.

Convert the moles of the first reactant to grams using its molar mass.

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 chemical equation. It involves using mole ratios derived from the coefficients of the balanced equation to determine how much of each substance is needed or produced. Understanding stoichiometry is essential for solving problems related to the amounts of reactants and products in a reaction.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a molecule. Knowing the molar mass of reactants allows for the conversion between grams and moles, which is crucial for stoichiometric calculations in precipitation reactions.

Precipitation Reactions

Precipitation reactions occur when two aqueous solutions react to form an insoluble solid, known as a precipitate. These reactions can be represented by balanced chemical equations, which show the reactants and products involved. Understanding the formation of precipitates helps in predicting the outcome of reactions and calculating the amounts of reactants needed for complete reactions.

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Selective Precipitation

Related Practice

Open Question

For each of the reactions, calculate the mass (in grams) of the product that forms when 3.67 g of the underlined reactant completely reacts. Assume that there is more than enough of the other reactant. a. Ba(s) + Cl2(g) → BaCl2(s) b. CaO(s) + CO2(g) → CaCO3(s) c. 2 Mg(s) + O2(g) → 2 MgO(s) d. 4 Al(s) + 3 O2(g) → 2 Al2O3(s)

Textbook Question

For each of the reactions, calculate the mass (in grams) of the product that forms when 15.39 g of the underlined reactant completely reacts. Assume that there is more than enough of the other reactant.

a. 2 K(s) + Cl₂(g) → 2 KCl(s)

b. 2 K(s) + Br₂(l) → 2 KBr(s)

c. 4 Cr(s) + 3 O₂(g) → 2 Cr₂O₃(s)

d. 2 Sr(s) + O₂(g) → 2 SrO(s)

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Textbook Question

For each of the acid–base reactions, calculate the mass (in grams) of each acid necessary to completely react with and neutralize 4.85 g of the base. b. 2 HNO₃(aq) + Ca(OH)₂(aq) → 2 H₂O(l) + Ca(NO₃)₂(aq)

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Textbook Question

Find the limiting reactant for each initial amount of reactants.

2 Na(s) + Br₂(g) → 2 NaBr(s)

a. 2 mol Na, 2 mol Br₂

b. 1.8 mol Na, 1.4 Br₂

c. 2.5 mol Na, 1 mol Br₂

d. 12.6 mol Na, 6.9 mol Br₂

Find the limiting reactant for each initial amount of reactants. 4 Al(s) + 3 O₂( g) → 2 Al₂O₃(s)

a. 1 mol Al, 1 mol O₂

b. 4 mol Al, 2.6 mol O₂

c. 16 mol Al, 13 mol O₂

d. 7.4 mol Al, 6.5 mol O₂

Consider the reaction: 4 HCl(g) + O₂(g) → 2 H₂O(g) + 2 Cl₂(g) Each molecular diagram represents an initial mixture of reactants. How many molecules of Cl₂ form from the reaction mixture that produces the greatest amount of products?

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