Chapter 21, Problem 98GQ

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074

Chapter
Section

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074
Textbook Problem

# Ammonium perchlorate is used as the oxidizer in solid-fuel rockets. Assume that one launch requires 700, tons (6.35 × 105 kg) of the salt, and the salt decomposes according to the equation on page 1005.(a) What mass of water is produced? What mass of O2 is produced?(b) If all the O2 produced is assumed to react with the powdered aluminum present in the rocket engine, what mass of aluminum is required to use up all of the O2?(c) What mass of Al2O3 is produced?

(a)

Interpretation Introduction

Interpretation:

To calculate the mass of H2O and O2 produced in the decomposition of ammonium perchlorate.

Concept introduction:

Ammonium perchlorate upon decomposition gives NO, Cl2 and O2 gases. It is used as the oxidizer in solid-fuel rockets.

The total number of moles of the substance is equal to the mass of the substance divided by the molecular weight of that substance.

The limiting reagent in the chemical reaction is the substance that is totally consumed when the chemical reaction is complete. The amount of product formed is limited by the limiting reagent.

Explanation

The mass of H2O and O2 produced in the decomposition of ammonium perchlorate is calculated below.

Given:

The mass of ammonium perchlorate is 6.35Ã—105â€‰kg.

The balanced chemical equation of decomposition of ammonium perchlorate is written as,

Â Â Â Â 2NH4ClO4(s)â†’4H2O(l)+O2(g)+Cl2(g)+2NO(g)Â Â Â Â  Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  (1)

The number of moles (nNH4ClO4) of ammonium perchlorate is equal to the mass of ammonium perchlorate divided by its molecular weight. The number of moles (nNH4ClO4) is calculated as,

nNH4ClO4=6.35Ã—108â€‰g117.49â€‰gâ‹…molâˆ’1=0.05Ã—108â€‰mol

From equation (1), two moles of ammonium perchlorate produced four moles of water molecules. Therefore, the number of moles (nH2O) of water molecules produced from 0.05Ã—108â€‰mol of ammonium perchlorate is written as,

nH2O=(4â€‰mol2â€‰mol)(0.05Ã—108â€‰mol)=0.108Ã—108â€‰mol

The mass (mH2O) of water molecule is equal to the product of a number of moles of the water molecule and its molecular weight

(b)

Interpretation Introduction

Interpretation:

To calculate the mass of aluminium which is required to use up all of the oxygen to form Al2O3

Concept introduction:

Ammonium perchlorate upon decomposition gives NO, Cl2 and O2 gases. It is used as the oxidizer in solid-fuel rockets.

The total number of moles of the substance is equal to the mass of the substance divided by the molecular weight of that substance.

The limiting reagent in the chemical reaction is the substance that is totally consumed when the chemical reaction is complete. The amount of product formed is limited by the limiting reagent.

(c)

Interpretation Introduction

Interpretation:

To calculate the mass of Al2O3 produced in the reaction of powdered aluminium with oxygen.

Concept introduction:

Ammonium perchlorate upon decomposition gives NO, Cl2 and O2 gases. It is used as the oxidizer in solid-fuel rockets.

The total number of moles of the substance is equal to the mass of the substance divided by the molecular weight of that substance.

The limiting reagent in the chemical reaction is the substance that is totally consumed when the chemical reaction is complete. The amount of product formed is limited by the limiting reagent.

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