   Chapter 20, Problem 90CWP

Chapter
Section
Textbook Problem

# Which of the following statement(s) is(are) true?a. The alkali metals are found in the earth’s crust in the form of pure elements.b. Gallium has one of the highest melting points known for metals.c. When calcium metal reacts with water, one of the products is H2(g).d. When AlCl3 is dissolved in water, it produces an acidic solution.e. Lithium reacts in the presence of excess oxygen gas to form lithium superoxide.

(a)

Interpretation Introduction

Interpretation: The authenticity of the given statement is to be determined.

Concept introduction: The alkali metals occur in the combined state and occur in the minerals in the earth’s crust.

The melting point of gallium is 29.76C , that is very close to the room temperature.

Reaction of calcium with water is,

Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g)

Reaction of aluminum trichloride with water is,

AlCl3(s)+3H2O(l)Al(OH)3(aq)+HCl(aq)

Lithium reacts in the presence of oxygen as,

4Li(s)+O2(g)2Li2O(s)

To determine: The authenticity of the statement, “The alkali metals are found in the earth’s crust in the form of pure elements.”

Explanation

The given statement is false.

The alkali metals occur in the combined state and occur in the minerals in the earth’s crust...

(b)

Interpretation Introduction

Interpretation: The authenticity of the given statement is to be determined.

Concept introduction: The alkali metals occur in the combined state and occur in the minerals in the earth’s crust.

The melting point of gallium is 29.76C , that is very close to the room temperature.

Reaction of calcium with water is,

Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g)

Reaction of aluminum trichloride with water is,

AlCl3(s)+3H2O(l)Al(OH)3(aq)+HCl(aq)

Lithium reacts in the presence of oxygen as,

4Li(s)+O2(g)2Li2O(s)

To determine: The authenticity of the statement, “Gallium has one of the highest melting points known for metals.”

(c)

Interpretation Introduction

Interpretation: The authenticity of the given statement is to be determined.

Concept introduction: The alkali metals occur in the combined state and occur in the minerals in the earth’s crust.

The melting point of gallium is 29.76C , that is very close to the room temperature.

Reaction of calcium with water is,

Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g)

Reaction of aluminum trichloride with water is,

AlCl3(s)+3H2O(l)Al(OH)3(aq)+HCl(aq)

Lithium reacts in the presence of oxygen as,

4Li(s)+O2(g)2Li2O(s)

To determine: The authenticity of the statement, “When calcium reacts with water, one of the product is H2(g) .”

(d)

Interpretation Introduction

Interpretation: The authenticity of the given statement is to be determined.

Concept introduction: The alkali metals occur in the combined state and occur in the minerals in the earth’s crust.

The melting point of gallium is 29.76C , that is very close to the room temperature.

Reaction of calcium with water is,

Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g)

Reaction of aluminum trichloride with water is,

AlCl3(s)+3H2O(l)Al(OH)3(aq)+HCl(aq)

Lithium reacts in the presence of oxygen as,

4Li(s)+O2(g)2Li2O(s)

To determine: The authenticity of the statement, “When AlCl3 reacts with water, it produces an acidic solution.”

(e)

Interpretation Introduction

Interpretation: The authenticity of the given statement is to be determined.

Concept introduction: The alkali metals occur in the combined state and occur in the minerals in the earth’s crust.

The melting point of gallium is 29.76C , that is very close to the room temperature.

Reaction of calcium with water is,

Ca(s)+2H2O(l)Ca(OH)2(aq)+H2(g)

Reaction of aluminum trichloride with water is,

AlCl3(s)+3H2O(l)Al(OH)3(aq)+HCl(aq)

Lithium reacts in the presence of oxygen as,

4Li(s)+O2(g)2Li2O(s)

To determine: The authenticity of the statement, “Lithium reacts in the presence of excess oxygen gas to form lithium peroxide.”

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