Ch.4 - Chemical Reactions and Chemical Quantities

Tro - Chemistry: A Molecular Approach 5th Edition

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Tro 5th Edition

Ch.4 - Chemical Reactions and Chemical Quantities

Problem 34

Chapter 4, Problem 34

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)

Verified step by step guidance

Identify the underlined reactant, which is Sr (Strontium) in this case.

Write the balanced chemical equation: \( 2 \text{Sr} (s) + \text{O}_2 (g) \rightarrow 2 \text{SrO} (s) \).

Calculate the molar mass of the underlined reactant, Sr, using the periodic table.

Convert the mass of Sr given (15.39 g) to moles using its molar mass.

Use the stoichiometry of the balanced equation to find the moles of SrO produced, then convert this to grams using the molar mass of SrO.

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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 branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It allows us to calculate the amount of product formed from a given amount of reactant using the coefficients from the balanced chemical equation. In this case, understanding the stoichiometric ratios is essential to determine how much strontium oxide (SrO) can be produced from the given mass of strontium (Sr).

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is crucial for converting between the mass of a substance and the number of moles, which is necessary for stoichiometric calculations. For the reaction provided, calculating the molar mass of strontium and strontium oxide will enable the conversion of the mass of strontium into moles and subsequently into grams of the product formed.

Balanced Chemical Equation

A balanced chemical equation represents a chemical reaction with equal numbers of each type of atom on both sides of the equation. It ensures the law of conservation of mass is upheld. In the reaction 2 Sr(s) + O2(g) → 2 SrO(s), the coefficients indicate that two moles of strontium react with one mole of oxygen to produce two moles of strontium oxide, which is essential for determining the amounts of reactants and products involved.

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Related Practice

Textbook Question

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

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Textbook Question

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?

Textbook Question

Hydrobromic acid dissolves solid iron according to the reaction:

Fe(s) + 2 HBr(aq) → FeBr₂(aq) + H₂(g)

What mass of HBr (in g) do you need to dissolve a 3.2-g pure iron bar on a padlock?

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

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Textbook Question

Hydrobromic acid dissolves solid iron according to the reaction:

Fe(s) + 2 HBr(aq) → FeBr₂(aq) + H₂(g)

What mass of HBr (in g) do you need to dissolve a 3.2-g pure iron bar on a padlock? What mass of H₂ would the complete reaction of the iron bar produce?

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