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The Determination of the Percent Water in a Compound

Introduction

The polarity of the water molecule, which makes it a great solvent for ionic compounds, causes water molecules to cling to the structure of solid substances. When this occurs, the trapped water molecules are called water of hydration and they become an integral part of the crystal structure.

There are many compounds that have a tendency to absorb water vapor from the air. These compounds are said to be hygroscopic, and can be used as moisture-reducing agents. Other compounds absorb such large quantities of water vapor that they will actually dissolve in their own water of hydration, a property known as deliquescence.

In this experiment, you will test a hygroscopic ionic compound to determine its water of hydration. Although the water molecules are securely attached to the ionic solid that you will test, they are susceptible to removal by heat. You will gently heat a sample of the compound to drive off the water of hydration. By measuring the mass of the sample before and after heating, you can determine the amount of water in the sample and calculate its water of hydration.

Objectives

In this experiment, you will

  • Carefully heat a measured sample of a hygroscopic ionic compound.
  • Determine the water of hydration of the compound.
  • Complete the chemical formula of the compound.

Sensors and Equipment

No probeware required for this experiment.

Standards Correlations

See all standards correlations for Advanced Chemistry with Vernier »

Advanced Chemistry with Vernier

See other experiments from the lab book.

1The Determination of a Chemical Formula
2The Determination of the Percent Water in a Compound
3The Molar Mass of a Volatile Liquid
4Using Freezing-Point Depression to Find Molecular Weight
5The Molar Volume of a Gas
6Standardizing a Solution of Sodium Hydroxide
7Acid-Base Titration
8An Oxidation-Reduction Titration: The Reaction of Fe2+ and Ce4+
9Determining the Mole Ratios in a Chemical Reaction
10The Determination of an Equilibrium Constant
11Investigating Indicators
12The Decomposition of Hydrogen Peroxide
13Determining the Enthalpy of a Chemical Reaction
14ASeparation and Qualitative Analysis of Cations
14BSeparation and Qualitative Analysis of Anions
15AThe Synthesis of Alum
15BThe Analysis of Alum
16Conductimetric Titration and Gravimetric Determination of a Precipitate
17Determining the Concentration of a Solution: Beer's Law
18Liquid Chromatography
19Buffers
20Electrochemistry: Voltaic Cells
21Electroplating
22The Synthesis and Analysis of Aspirin
23Determining the Ksp of Calcium Hydroxide
24Determining Ka by the Half-Titration of a Weak Acid
25The Rate and Order of a Chemical Reaction
26The Enthalpy of Neutralization of Phosphoric Acid
27α, β, and γ
28Radiation Shielding
29The Base Hydrolysis of Ethyl Acetate
30Exploring the Properties of Gases
31Determining Avogadro's Number
32Potentiometric Titration of Hydrogen Peroxide
33Determining the Half-Life of an Isotope
34Vapor Pressure and Heat of Vaporization
35Rate Determination and Activation Energy

Experiment 2 from Advanced Chemistry with Vernier Lab Book

<i>Advanced Chemistry with Vernier</i> book cover

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