Ch.1 - Introduction: Matter, Energy, and Measurement

Problem 17

Chapter 1, Problem 17

A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance B and a gas C. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these observations, can we determine whether solids A and B and gas C are elements or compounds?

Verified step by step guidance

Identify the gas C by comparing its properties to the known product of carbon burning in excess oxygen. When carbon burns in excess oxygen, it forms carbon dioxide (CO\_2), which is a compound, not an element.

Since gas C has the same properties as carbon dioxide, conclude that gas C is carbon dioxide, a compound.

Analyze the decomposition reaction: solid A decomposes into solid B and gas C (carbon dioxide). This suggests that solid A contains carbon and oxygen atoms combined in some way.

Because solid A decomposes into two different substances (solid B and gas C), solid A must be a compound, not an element.

Solid B is a new white substance formed after the release of carbon dioxide. Since it is different from A and formed by decomposition, solid B is also likely a compound, not an element.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Thermal Decomposition

Thermal decomposition is a chemical process where a compound breaks down into simpler substances when heated, often in the absence of air. It helps identify whether a substance is a compound by observing if it splits into different products upon heating.

Identification of Gases by Properties

Gases can be identified by comparing their physical and chemical properties to known substances. For example, carbon dioxide (CO2) is produced when carbon burns in oxygen, so a gas with identical properties is likely CO2, indicating the nature of the gas released during decomposition.

Distinguishing Elements from Compounds

Elements are pure substances that cannot be broken down further by chemical means, while compounds consist of two or more elements chemically combined. Observing decomposition into different substances indicates the original solid is a compound, while the products may be elements or compounds depending on their composition.

Recommended video:

Guided course

02:35

Elemental Forms of Elements

Related Practice

Textbook Question

Give the chemical symbol or name for the following elements, as appropriate: (f) Sb (g) Pb (h) Br (i) V (j) Hg.

Textbook Question

Give the chemical symbol or name for each of the following elements, as appropriate: (a) rhenium (b) tungsten (c) cesium (d) hydrogen (e) indium

views

Textbook Question

Give the chemical symbol or name for each of the following elements, as appropriate: (f) As (g) Xe (h) Kr (i) Te (j) Ge.

Textbook Question

Zirconia, an oxide of zirconium, is often used as an affordable diamond substitute. Just like diamond, it is a colorless crystal which sparkles under sunlight. Which of the following physical properties do you think would help in differentiating between diamond and Zirconia—melting point, density, or physical state?

In the process of attempting to characterize a substance, a chemist makes the following observations: The substance is a silvery white, lustrous metal. It melts at 649 °C and boils at 1105 °C. Its density at 20 °C is 1.738 g/cm³. The substance burns in air, producing an intense white light. It reacts with chlorine to give a brittle white solid. The substance can be pounded into thin sheets or drawn into wires. It is a good conductor of electricity. Which of these characteristics are physical properties, and which are chemical properties?

views

rank

Textbook Question

The radius of an atom of tungsten (W) is about 2.10 A . (a) Express this distance in nanometers (nm). Express this distance in picometers (pm).

views