   Chapter 21, Problem 36PS

Chapter
Section
Textbook Problem

Calcium reacts with hydrogen gas at 300–400 °C to form a hydride. This compound reacts readily with water, so it is an excellent drying agent for organic solvents. (a) Write a balanced equation showing the formation of calcium hydride from Ca and H2. (b) Write a balanced equation for the reaction of calcium hydride with water (Figure 21.7).

(a)

Interpretation Introduction

Interpretation: To write the balanced chemical equation of the reaction of formation of calcium hydride from calcium and H2

Concept introduction: The reaction of elements with hydrogen produces either ionic metal hydrides or molecular compounds.  The reaction of hydrogen with metals produces ionic metal hydrides. The electronegativity of hydrogen is more than metals and hence, metals bear positive charge and hydrogen has a negative charge. Thus, the oxidation number of hydrogen in ionic metal hydrides is 1.

The reaction of calcium and hydrogen forms calcium hydride. The reaction occurs at 300400 degrees temperature. Calcium hydride is very reactive compound and reacts violently with water to produce hydrogen gas and calcium hydroxide. Thus, it is used as a drying agent for organic solvents. The hydrogen and calcium hydroxide is separated by the process of filtration or distillation.

Explanation

Calcium belongs to group 2A of the periodic table. Hence, the highest oxidation number is +2. There are two valence electrons in the outermost shell of calcium. Calcium loses these two electrons to attain noble gas configuration. Thus, the oxidation number of calcium is +2. The electronic configuration of calcium is: [Ar]4s2.

Hydrogen has an oxidation number of +1 or 1, depending upon the electronegativity of the element to which it is attached. Calcium is more electropositive, so the oxidation number of hydrogen in this case is 1

(b)

Interpretation Introduction

Interpretation: To write the balanced chemical equation of the reaction of calcium hydride with water.

Concept introduction: The reaction of elements with hydrogen produces either ionic metal hydrides or molecular compounds.  The reaction of hydrogen with metals produces ionic metal hydrides. The electronegativity of hydrogen is more than metals and hence, metals bear positive charge and hydrogen has a negative charge. Thus, the oxidation number of hydrogen in ionic metal hydrides is 1.

The reaction of calcium and hydrogen forms calcium hydride. The reaction occurs at 300400 degrees temperature. Calcium hydride is very reactive compound and reacts violently with water to produce hydrogen gas and calcium hydroxide. Thus, it is used as a drying agent for organic solvents. The hydrogen and calcium hydroxide is separated by the process of filtration or distillation.

Still sussing out bartleby?

Check out a sample textbook solution.

See a sample solution

The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started 